This book had a considerable influence on my career choice. It was difficult to find a book that described the design of a compiler in such a practical way. I now develop compilers, and new programming languages, and I owe it to Mr. Watt and Mr. Brown. Some more advanced concepts are not covered in the book (that remains a 'must have') like dataflow analysis, SSA, polyhedral analysis, but there are plenty of books about that (Cooper & Torczon, Aho & Sethi, etc).