Did you ever notice that these marvelous particles i, e, të, së, which link postposed adjectives to their head nouns, are also used to form the postposed genitive construction. In both cases the choice of particle depends on the number, gender, and case of the preceding head noun.
But it also brings up a huge question: how can you call the Albanian genitive construction a case when the particle that introduces the genitive is itself inflected for case? The simple answer is, the genitive is not a case, but rather a construction analogous to the noun+adjective construction. In the genitive construction, the linking particle agrees with the preceding head noun in number, gender, and case (as in the noun+adjective construction), and is followed by a noun in the dative case.
Here's a way to parse these two constructions mentally: translate the linking particle as "which [is/are]". So, for example: libri i mirë "the-book which-is good" = "the good book", librit të mirë "to-the-book to-the-one-which-is good" = "to the good book".
Likewise in the genitive construction: libri i njeriu "the-book which-is to-the-man" (i.e. belonging to the man) = "the man's book", librit të njeriut "to-the-book to-the-one-which-is to-the-man" = "to the man's book".
And in fact it appears likely that these linking particles are historically weakened forms of the old demonstrative stem that underlies the modern ai, ajo "he, she; that one" and ky, kjo "this one". This stem can be found by taking the initial a- off of ai, ajo, and the initial kë- off of all forms of ky, kjo except for the nominative m.sg. and f.sg. So we find m.sg. i, f.sg. jo (or an earlier form of it) could have been weakened to e; të comes from accusative të or masc. dative tij and was generalized to the plural; së comes from fem. dative saj. At one point they evidently came to be used as relative pronouns "(that/those) which" as well as plain old demonstratives--"that/those".
And ultimately they became essential components both types of attributive constructions: (1) head noun modified by postposed adjective and (2) head noun modified by postposed dative-case noun, also known as the genitive construction.