I also use PostgreSQL Developer's Handbook published by Sams. It is written
in a more reference format. I haven't looked at the Wrox PostgreSQL book but
I have used their books for PHP. I would only go with Wrox if you choose a
book from their pro series. Their beginner books are too class room like.
The Majority of the PostgreSQL Developer's Handbook covers PostgreSql
Administration, features, and programming interfaces. It only covers the
basics of sql which it sounds like you could skip. I highly recommend the
book. I don't think you could go wrong with it, especially using it in
conjunction with the PostgreSql website. Although, I doubt you would go
wrong with any of the books from the major publishers either. The advantage
of Momijan's book is that you get the word straight from the developer's
mouth. The disadvantage I found from previewing it online is that it is very
similar to the online documents so you don't get as much of a variety in the
way things are explained.
Julie
P.S. Let us know what you go with and what you think.