The bible of the field, but very dense. It's simply a collection of seminal papers.
If you want to learn computational geometry as a beginner, better read:
- Shamos' PhD thesis
- O'Rourke's books (one of them has implementations in C as well)
- Mark de berg et al.
If you want to dive deep into theory, a la francais, try J-D Boissonat's et all book.
They are all French, so this is much harder and deeper, imho, than the Preparata-Shamos book. Not for the faint hearted.