Elvstrøm produces great sails which should give you great performance and add enjoyment to your sailing. But like most activities, this enjoyment can be increased by knowing how they should be used.
Getting the best out of your sails is important whether racing or cruising - you should want your sails to be producing their best for you, and its not so difficult to do so.
The Sail Trim "book" is an overall view of upwind and downwind sailing - for both cruising and racing. It tries to give a clear description of the conditions, and then how to set the sails. There is some theory, but it can be skipped over, and the "Power Levels" pages give clear practical tips on what to do with the sails and rig.
The Swan 45 and X-35 "books" give set-up and tuning tips, and more boats will follow. However, they are worth reading even if you dont have either, since the concepts can be applied to many modern boats in general terms.