I like both styles.
What you could do is "hiding" the books on different locations.
Type I would be found in "high end buildings" (dungeons) like Tortage Underhalls, Sanctum of the Burning Souls, Toirdealbach's Tomb, Onyx Chambers.
Type II would be found in more private locations like Coastal Cave, Bubshur House, "Noble Villa's", Slaughterhouse Cellar.
Both should ofcourse also be found at unlikely open world locations to promote exploration.
Books should come in various degerees of rarity like armor and weapons: Mundane, Rare and Unique
Books should not be "bound" to locations unreachable for veteran toons (Destiny-quest dungeons, white sands)
Finding X Mundane/Rare/Unique books should give an achievement/title: "The Librarian" maybe?