Pleasure.

Schrödter, Don Quixote, Reading in the Armchair, 1834

I believe that the phrase "obligatory reading" is a contradiction in terms; reading should not be obligatory. Should we ever speak of "obligatory pleasure?"  Pleasure is not obligatory, pleasure is something we seek. "Obligatory happiness!"

If a book bores you, leave it; don’t read it because it is famous, don’t read it because it is modern, don’t read a book because it is old. If a book is tedious to you, leave it, even if that book is Paradise Lost — which is not tedious to me — or Don Quixote — which also is not tedious to me. But if a book is tedious to you, don't read it; that book was not written for you. Reading should be a form of happiness, so I would advise all possible readers of my last will and testament—which I do not plan to write— I would advise them to read a lot, and not to get intimidated by writers' reputations, to continue to look for personal happiness, personal enjoyment. It is the only way to read.

Jorge Luis Borges