A log book service is supposed to do the recommended items listed in the log book which are based on the mile age or the life of your car(service intervals) , i.e. for 100k most manufactures suggest that the timing belt be changed, etc. When you present your log book, the service people will normally do the items suggested in it and they will stamp it to record the service as well.
Other services depend on what you want to do, for example if you want to have a service every 5,000kms you can do that.
A log book is the service manual of your car. Hope this will help.