"I like books."
Translation:J'aime les livres.
Because here "I like books" means "I like books in general" which is translated in french by "Les livres". "Des" means "some".
"Les lapins" = Rabbits (in general)
"Des lapins" = Some rabbits
I like the books does not specify particular books, therefore the answer is "J'aime des livres" I like books FULL STOP! It is impossible to see that I like books means books in general. You have a lot of this type of error/deliberate confusion!!!
The reason you choose "J'aime les livres" instead of "J'aime des livres" is because aimer is a verb of appreciation - to like. When ever you have an object following a verb of appreciation such as aimer, you use les instead of des.