This little (and long-out-of-print) book is an amazing description of the actual engineering associated with building an optimizing compiler for the Bliss-11 language. It's also interesting in that many of the co-authors (Wulf's PhD students) have gone on to develop significant software products.

It got me started in compilers over 30 years ago, and I've been doing language design and code generation for most of the time since.

Another suggestion is to check the ACM website. A couple of years ago they ran a contest to find out-of-print classics and arrange to get the top N of them reprinted.