I always by O'Reily when I'm buying a reference book.

This is well written as all O'Reilly books are.

BUT: It's almost usless. I'm using RCS the book
is very confusing mixing RCS & SCCS in the same
chapters. It also needs a better index, it suffers from the confusion.

It's OK to have the two systems in the same book
BUT they should be in seperate sections.