Before just using them all to gain knowledge, know that they have another use.
You can turn them in at a shelf near the original Map Room in the unnamed city. That will teach you a new recipe for a weapon, Tablet of Power, Fast Elevators, etc. There are a finite number of recipes obviously, so once you know them all, they have no use there anymore.
Second, you can just use one directly to gain knowledge points. The Tablet of Power I mentioned is a recipe learned from turning them in as noted above.

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