Within the body of your essay --
Titles in which the first letter of each word is capitalized:
Games People Play
Girl, Interrupted
Titles that include:
-- coordinating conjunctions (and, or, for, nor, or, but, so)
-- articles (a, an, the)
-- prepositions (in, on, as, for, from, of, with, etc.) :
Love in a Cold Climate
Life of Pi
Those Who Leave and Those Who Stay
Books with subtitles:
Possession: A Romance
The Tipping Point: How Little Things Can Make a Big Difference
In the reference list --
Books with subtitles:
Beyond words: What animals think and feel
Quiet: The power of introverts in a world that can’t stop talking
Books without subtitles:
Ulysses
Under the net
Titles that include a proper noun:
Cassell’s French dictionary
A linguistic guide to English poetry
Three Junes