Book recommendations

I have the second edition of Pro Drupal Development, and it's undoubtedly the standard text for Drupal 6. The reviews on amazon.com were pretty negative about the third edition, though. It sounds like it was a rush job, and they didn't devote enough time to explaining the unique features of the Drupal 7 API. Large sections of the book probably needed to be rewritten to give the changes from Drupal 6 to 7 a proper treatment. Drupal 7 Module Development, on the other hand, got great reviews, and they were well deserved, in my opinion. I liked the way D7MD is briefer and structured like a tutorial, rather than an exhaustive subsystem-by-subsystem survey of the API. Drupal's online docs are adequate, and the Drupal source code is fairly easy to read, so I think it was a smart choice to skim the details and not worry about collecting all the information on each subsystem in its own chapter, so that the book can be used as a reference. It's not necessary to have a book you can use to look up details, because the information is all online. Somehow the D7MD book seemed to offer insight into the logic of the new API, as opposed to just explaining how to use it, possibly in part because it was a brand new book and not an updated version of a book written for an earlier version of Drupal. Even though it's terse -- by computer book standards -- I found myself having to reread some chapters several times to get it all, and sometimes study the online docs and painstakingly cross-reference all of the information before I felt like I really, truly got it. So it took a long time to read, but I would rather have short chapters that I can reread multiple times at my option than a slow, plodding pace throughout the whole book. All of that being said, I was glad for the half of Pro Drupal Development 2nd ed. that I had managed to read previously, because it enabled me to breeze through some parts of D7MD that hadn't changed very much.

I have the O'Reilly vi and Vim Editors Pocket Reference, but I haven't got around to spending much time with it. It has been mostly sitting on my shelf, unread, simply because I haven't felt like learning more Vim, not because I don't think it's good book. So, I don't have a very good idea of what goes into one. What would be in it? A list of the API functions, along with brief descriptions? My feeling is that Drupal is too complex to learn it from that kind of book, unless you have experience with similar software (is there any?).* The API docs on drupal.org are decent, as long as you already have a pretty good idea of what the functions do and how they fit into the Drupal way of doing things. I personally think that the docs could be better organized online, and as a little personal project, I am creating a website that aims to provide better access to developer documentation. Mostly a hierarchical collection of links, sort of like what Yahoo started out as. I might also add a wiki or something equivalent and whatever else I get around to doing. The project is mostly for me to gain experience setting up a working Drupal site, but I am hoping it will become something more. It's still in very early development (I started it this morning).

* I just remembered that you said you are familiar with the Drupal 6 API, so it's conceivable that you would be able to upgrade your knowledge from a small book. But how big would the market be?