I buy the factory service manuals for all the vehicles that I own.
Reason is that quality service is hard to come by and I do almost all my own service.
Granted I only buy GM vehicles now (I used to work for Nissan) so I don't know what all these folks offer. Anyway these are the real McCoy of Vehicle Service Manuals. Cost is up there too, for my Vette a stack of 3 books was about $125.00, my P/U was $150.00
Helm Publications Division
14310 Hamilton Ave.
Highland Park Mi 48203
I'll try to get ya a phone number, I'm looking at my receipt now and there's not one on it.
The original place I got the info was in the owners manual of my cars in the back. There I found a phone number but don't have the time to retrieve it now, gotta run.

)