Whenever any enchanted books are found in desert temples (pyramids) in version 1.7.4, the book will have 3 completely different random enchantments on it.
In addition, and this is a hypothesis, multiple enchanted books found in the same chest will have the exact same three enchantments on them.
This can be seen in seed: 4103936076635780841
Version 1.7.4
(Default world, no large biomes)
Coordinates of the temple are: -837 84 204
An additional example can be seen in seed: 76697780408410142
Version 1.7.4
(Default world, no large biomes)
Coordinates of the temple are: 603 74 -932
Yes, that's a thing now. That you found two Desert Temples with such books is just pure luck.