the fourth one , dear zed poem

You'll find these in the page source;

no spaces, all lower-case, no puntuation, as usual
you'll find in this world, most things are capitalized for a reason
i said, "behave nick."

Think acronyms.
i said, "behave nick" has the acronym ISBN. What does that remind you of? Books. About capitalizations, usually after ISBN there are numbers, so obviously you would now require numbers, with the help of the poem.
Note the capitalized words. The first two letters of capitalized words represent numbers. Si= Six, Ei= Eight
You will find that the code is "ISBN 0061238600"
Google the code.

You need to know who the book was dedicated for. If you read books , you'd know that they usually write
"for blablabla" somewhere on the first few pages of the book. So, go search the book. Don't have the book? http://www.harpercollins.com allows you to read the first few pages books. GO now.
The answer is mymotherandfather (highlight to expose)

P.S. As you may already know, ThisIsNotTom was created by John Green back in 2009. He's now a best selling author. The movie The Fault In Our Stars was based on a book by him. If you liked TINT and also The Fault in Our Stars, you should check out the book that made me cry when I was supposed to be a super macho teenage boy, Looking for Alaska. You can get it here.