Object-relational mapping is a fact of life for most people, so it's no surprise that there's been a lot written on the subject. The surprise is that there isn't a single coherent, complete, and up-to-date book, which is why I've devoted so much of this one to this tricky yet interesting subject.
The nice thing about database mapping is that there's a lot of ideas out there to steal from. The most victimized intellectual banks are [Brown and Whitenack], [Ambler], [Yoder], and [Keller and Coldewey]. I'd certainly urge you to have a good surf through this material to supplement the patterns in this book.