Five Ancient Kingdoms is an Arabian Nights flavored game with the scope and presentation style of OD&D. Mechanically, it uses a Chainmail-inspired 2d6 resolution system. It manages to pack a tremendous amount of content into a very small word count. Five Ancient Kingdoms is probably on my short list of good intro RPGs (along with the Pathfinder Beginner Box and Lamentations of the Flame Princess).
My reaction has been almost entirely positive, but there are a few aspects that I am critical of, so let’s get them out of the way first. Yes, I suspect that “Dragon Master” was used because JB wanted to write DM, but do we really need another term for game master? “Opposite sex” language is used in the romance rules, and that is unnecessarily limiting. There are no indexes, and no “appendix N” or recommended reading section (something that a pseudo-historical setting like Barica could greatly benefit from). There are a few places where rules were hard for me to find (for example, how damage against PCs works is in the Hit Dice section rather than the Damage section). The numerous passages with “as explained in book X” would benefit from page numbers.
On to the good stuff. The entire game is approximately 150 digest sized pages in three saddle-stapled booklets. This is bigger than the OD&D three little brown books, but not by much. I find the rules as written to be very similar to how I have come to house-rule my own OD&D game. Some examples. Death is handled with save or die at zero HP (though 5AK also leaves survivors of the death save with a major wound). HP are rolled anew each session. Encumbrance is not quite as simple as my one item per point of strength, but it’s not too bad (it uses a simple list of penalties based on commonly carried or equipped items).
The core is built around four classes that you will probably recognize: hero, magician, saint, and thief, though the abilities are balanced between them slightly differently than in the traditional game (mostly for the better, I think), and all without resorting to weapon and armor restrictions. The best martial weapons (sword and bow) require training to attack without a penalty, and this is handled mostly at the class level, which is a decent way of distinguishing the hero class.
As mentioned above, the resolution systems are based on Chainmail, and use 2d6. In fact, the entire game only uses six sided dice (though results of 1 are always treated as zero, to simulate something like the d20’s natural 1). There is no AC as such; instead, attack target numbers are 6 + HD + armor (which is +1 for light armor and +2 for heavy armor). The attack roll is 2d6 + melee bonus, which is class based (+ HD for heroes and + half HD for all other classes). There is no initiative, and attacks are handled in order of attack roll (highest first). This seems extremely elegant. I have been leaning towards something similar in my own systems recently, with HD as attack bonus (and, potentially, as AC too).
Monsters don’t have HP, and instead take “hits” (which are the equivalent of what would be a hit die worth of HP in trad D&D, just without the randomization). PCs do have HP (and monsters use the familiar 1d6 damage per hit against them). This sounds somewhat complicated, but it is clear in the booklets, and I imagine the streamlining works well in practice (though it also means that monster danger is a bit less variable). Armor also has a limited per-session ability to negate several hits. In terms of system, the only significant lack I see is an absence of something like an ability check to resolve arbitrary actions (something like roll under an ability score with 3d6 would work).
In addition to expected mechanical features, PCs also have a motivation, which is rather freeform (but many examples are provided), and motivation interacts with a number of subsystems, including XP (for example, achieving a milestone appropriate to motivation can vault PCs instantly to the next level). Characters have the option to push actions based on their class and motivation, which allows relevant actions to be attempted with three dice, take two best, but with a greater chance of catastrophe. It reminds me of this stunt system I proposed a while back, though JB’s version is only usable for class- or motivation-relevant tasks. The XP system is rather overcomplicated for my tastes, but then I am sort of a radical minimalist in this area (I really don’t want to bother tracking things like +1000 XP for the first time an artifact is used properly). The romance rules look promising, though they require players to disclaim some amount of PC control (there are chances to become smitten with an NPC, for example). This would add an interesting twist to standard D&D adventures, and romance is certainly integral to the original Arabian Nights tales.
In only six digest-sized pages, JB has managed to craft elegant subclass and feat systems (though his feats are called advantages, which is actually a much better name; I’ve always disliked the use of the word feat for granular abilities in third edition and after). There are 8 subclasses provided, and they work by swapping out base class abilities. For example, the mountebank is a thief subclass with minor magical abilities. The trade-off is fewer thief skill points in exchange for having the basic spell casting abilities of a first level magician, though the mountebank’s skill with magic does not improve. Advantages include things like smart pet, ogre-kin, and tracker. There are 36 advantages (a D66 table, actually), and they are each described using no more than a few sentences. The text suggests gaining an advantage at levels 1, 4, and 8. Both of these systems could probably be easily hacked into your clone of choice.
Magic is also handled somewhat untraditionally. Magicians use a spell casting roll, which is 2d6 + level (+1 for exceptional intelligence), versus a target number of 2 * spell magnitude (which is what would be called spell level in many other games). Saints call “miracles” using a per-adventure slot system, which is more or less Vancian, though miracles do not need to be chosen beforehand. The spells themselves are mostly recognizable variations on traditional spells (charm, illumination, beast speech, and so forth), though there are a few notable additions (such as the second magnitude gale), and some of the spells have had their power adjusted (for example, sleep only works against “passive/non-hostile targets”). This is somewhat important, because the roll-to-cast system target numbers make casting spells very easy (if you do the math, the only way to fail casting a first magnitude spell, even as a first level magician, is to “zero out,” which has a 1 in 36 chance). It seems like even casting high level spells would rarely fail; consider an 8th level magician casting the 5th magnitude cloud of death: 2d6 + 8 >= 14, which is approximately 72% chance of success (and spells are not exhausted when cast). I would seriously consider increasing the spell target numbers, perhaps to 7 + magnitude rather than 2 * magnitude, though I would like to see the original system in play first.
The setting itself is pretty generic, and mostly consists of Hyboria-style renaming of historical cultures and features (Salama rather than Islam, Rhyma rather than Rome, Bagdabha rather than Baghdad, and so forth). There are no maps, but the monster cosmology has been carefully crafted to reflect the source myths. Equipment is almost identical to the three LBBs, though, which is perhaps a wasted opportunity for introducing more Arabian aesthetic (why not janbiya rather than dagger, for example?). All illustrations are by Henry J. Ford, from Andrew Lang’s version of the Arabian Nights.
The discipline required to fit the entire game into this structure has resulted in a very streamlined, concise game. The organization could perhaps be slightly improved (I found myself hunting around for various rules clarifications while writing this overview), but the system itself is well written and simple enough that I don’t think this would be a problem in practice after running a few actual situations. You can buy Five Ancient Kingdoms in print at B/X Blackrazor (Paypal link in the upper right). All booklets are also available in PDF from RPGNow (Men & Mettle, Magic & Monsters, Dragon Master Secrets, intro adventure: Sorcerer Island).
Edit: added links to the other PDFs after they went live.