Well, maybe it`s just me, but I think if a book is advertised as a repair manual with specific engines listed, see below, it`s reasonable to assume that the reader will find a bit more information than how to remove the valve cover and replace the spark plug seal. Nothing about timing, nothing about replacing chain pads, etc. Things that are actually part of maintanance in these cars.
Porsche Repair Manual: Porsche Boxster, Boxster S: 1997-2004: Service Manual ****-**** Bentley Publishers - Repair Manuals and Automotive Books
Engines covered in this Porsche repair manual:
1997-1999 Porsche Boxster: 2.5 liter (M96/20)
2000-2004 Porsche Boxster: 2.7 liter (M96/22, M96/23)
2000-2004 Porsche Boxster S: 3.2 liter (M96/21, M96/24)