In case the OP is a console player without the advantage of addons...the only lore books that will increase your MG are the "Shalidor's Library" lorebooks...the purple/blue ones.
In case the OP is a console player without the advantage of addons...the only lore books that will increase your MG are the "Shalidor's Library" lorebooks...the purple/blue ones.
Also, these are the books that disappear when you read them. The regular Lore books stick around.
If you are on a console and don't have the add on to show where the books are, just note that there are 4 copies of almost every Blue Lore book in a zone, usually grouped in the same area. So, it's fairly easy to find them, especially at night as you can see the glow from quite a distance.