Rating: 

As it says on the cover, it's biased towards Solaris(8) and Linux. It tells you how to configure the various critical resources (i.e. processors, memory, page and swap, disk, RAID etc.) and most importantly, it tells you why you're doing it. The authors also encourage you to use the book as a start point and and experiment with resource configuration to find out what works best for a given workload. There is also a lot of underlying information about processors, memory and interfaces (IDE and SCSI) that is very useful. The Linux info is good too but this edition doesn't cover Solaris 9. This isn't a problem because for performance/tuning purposes, there isn't much difference between Sol 8 and 9).

I haven't given it a definitive rating because with performance tuning, there is no such thing as definitive. But it's close.

A great book and highly recommended. Many thanks to the authors.