The Hero Books.
Choose one of these books and place it next to your bed. You need ONE book for the journey, just one because you are going to be in an intimate and monogamous journey with this book during the ninety days. Yes, you may have afternoon trysts with other books, and flirtations, but you will need to be faithful to one book during your writing of your novel. Every night, please. Even if just for ten minutes before bedtime. Put that prose and the big story shape inside your mind and sleep on it. I promise you it works. Between that and the morning writing routine, you'll become a novel-writing machine.
This faithfulness mirrors the devotion you will show to your novel and helps you focus.
You'll read it once for pure pleasure, and absorb the storyline. (Story, story, story.) When you're reading it for the second or third time, you'll be deep in your own story, and will turn to it for assistance with technical problems. Your close study and profound understanding of how a great book works will give you skills to last a lifetime.
The Hero Book is a key success factor. Be careful about other books you choose to read during your writing period. You might lose sight of your own theme and lose the ability to hear your own voice. Worse, you will start to worry your work isn’t as good as Tom, Dick and Kafka’s and you will get miserable.
Leaning on just the one book allows you to keep your own work in mind. It’s like listening to the same song over and over again until you no longer hear any idiosyncrasies; you’re just feeling the song.
This is not an unusual method for a working novelist, in fact, it is quite common. Norman Mailer, when writing The Naked and the Dead, would constantly re-read Anna Karenina for inspiration.