This is the first book I have seen that looks clearly and concisely at effective Oracle development. Tom's discussion for example of the use of bind variables is both entertaining and informative. Similarly the comparative discussion of locking mechanisms and the impact that differing implemetations of this have on effective coding is essential reading for all of those developers tempted down the 'one approach suits all databases' road. All of this detailed technical knowledge is explained and illustrated with examples that you can easily run yourself to verify the impact that effective coding could have on your own applications.
Just as Jonathan Lewis' book should really be made available to all the DBAs in your organisation, so too should this book be on the developers bookshelf (or better yet desks).
A word of caution, though. It's really geared more toward the architect or DBA than it is the application developer.
Also, this is an advanced book that assumes some prior experience with Oracle. Not a good book for beginners.