The Cathedral and the Bazaar was not an excellent piece of writing, but it was sort of necessary at the time. It has served its evangelical purpose well, to the point where it's no longer necessary. Open Source won the day, in no small part due to ESR. (I think it vital to give my enemies their due praise).

TAoUP is a good book on the Unix Philosophy, but it's worth noting that the ultimate expression of these ideas (Plan 9) was a failure, and the 'everything is a file' metaphor is arguably incorrect. I hope I didn't give the impression that it was not worth reading, especially in the sense that there are few other good sources for that information (even using Unix is not likely to teach you much about its whys and wherefores). I just think that it should be read in the proper context, and that recommendations should try to include that context.