Yesterday I bought a present for Angela and I: a copy of the Rules Compendium. The book compiles rules from various sources into an easy to read format that is alphabetized by topic. Intermixed are essays on rules-design and anecdotes about how rules resolved into their current form. I think it will be good for both of us, but in wholly different ways.
For Angela, it will primarily be useful as a reference in her D&D game. She’s not a rules expert. It is often easier for her to wing it than to look up how an obscure rule works. Having all the rules for a topic on an easy-to-find page will make her life easier. (Honestly, she was happy that she could just turn to “S” and find all the Size rules… as she can never find them when she’s looking for them.)
For me, I think the essays will be the best part. The few I’ve read are pretty neat. Also, I think the book as a whole is worthwhile to look at in terms of a method of presenting rules.
As far as content goes, I have mixed reviews so far. The breadth of topics covered is pretty good. The depth, however, is inconsistent. Some areas are fairly deep. Others really just scratch the surface. Take the Mounted Combat section for example: there is no discussion of how Attacks of Opportunity work while mounted and there is no summary of the Mounted Combat Feat (despite the fact that most mounted NPCs are likely to have it). On the other hand, there is a very extensive table, broken up by action type, of actions you can take in combat. The table lists whether or not the action provokes an AoO and what page in the book includes more detail about that action. The table is also extensively footnoted.