Is the Book a Requirement?

"If you're really serious about looking for the treasure, get TTOTC and read it, and then go back and read the poem over and over and over again, and then go back and read the book again but slowly, looking an..looking at every little abstract thing that might catch up in your brain, that might be a hint to help you with the clues. Any part of some is better than no part of any. f"

In this, Fenn makes it clear - at least to me - that if you are serious about solving the poem and looking for the treasure, you absolutely must have the book, The Thrill of the Chase.

I believe now that there are reasons why he's repeatedly said similar - to read the poem, read the book, go back to the poem, etc.

The book helps you understand HOW to solve the clues in the poem.  

For example, in the book, Fenn gives a lot of different ways to understand the word "brown" - from browning pies in the oven, to the color of the stain on his pants when he slid down the fire escape.  This helps us understand the roll of synonyms and word usage in the poem because a word like "brown" can means many things; our job is to tease out what it means in the poem, and the book gives us examples of not only what brown can mean, but also how Fenn uses it in different contexts.

So, is the book a requirement to solve the poem?

At this point, I do believe it is required to solve the poem; it's available from Collected Works in Santa Fe, NM.