Did the books Holdon read influence his intellectual development?
Of course they did. How could they not? Every single person or thing...no matter how small the item or insignificant the connection...that we encounter as humans has a distinct effect on us and the way we see the world around us. You may not notice the effect until much later, but every person, book, event, happenstance, etc. works to shape us in some way as people. This is especially true for books and poems that we read carefully. One cannot help but imagine we are the main character and how we would deal with similar situations should we ever find ourselves in their shoes. We are the culmination of our experiences.
For instance, Holden begins the novel with a rather long speech about how he would not be like David Copperfield from the novel of the same name. Copperfield was born with a "caul," or the amniotic sac still in place over his body. This, to Holden, indicates that Copperfield did not intend to separate from his mother or his parents, but stay sheltered and close to home. In fact, stay connected in the closest possible way...to his mother and father. No, Holden will not be sheltered. He will not be bamboozled into believing what others tell him...he will not be victim to the phoniness of parental protection or of society's whims. He will go out and find the truth on his own. This book then, was very influential on our young protagonist.
Likewise, the poem by Robert Burns "Comin' Through the Rye" has a profound impact on Holden. Holden hears the line of the poem incorrectly: "Gin a body meet a body/ comin' through the rye." He thought it was, "Gin a body catch a body/ comin through the rye." This is where he decides to become a "catcher in the rye" as he imagines a rye field on the side of cliff with little children playing in the field. He wants to protect the children by standing on the edge of the field, catching them before they tumble over the cliff's ridge.
These are just two examples of readings Holden speaks of in his narrative, but I think it is clear that he is absolutely molded and changed as a result of these pieces.
The books Holden read did influence his intellectual development, that is why it is so sad that he keeps failing out of one school after another because he is so capable. It is not his intellect that is holding him back, it is his emotional trauma and unresolved crisis that keep Holden locked in isolation and unable to participate in school.
Holden does well in only one subject at Pencey, English. He tell us that he is familiar with the curriculum in English because it is the same as his former school.
"I passed English and all right. I said because I had all that Beowulf and Lord Randal My Son stuff when I was at the Whooten School." (Salinger)
Holden spends a lot of time reading. For example, he has taken a book out of the library, and he got the wrong book, but he read the book anyway.
"They gave me Out of Africa by Isak Dinesen. I thought it was going to stink, but it didn't. I read a lot of classical books, like The Return of the Native and all and I like them and I read a lot of war books and mysteries and all, but they don't knock me out too much." (Salinger)
As a reader, Holden developed his intellect and was capable of getting really good grades. The more you read, the greater your comprehension, not only in subjects in school, but in understanding the world. It is possible that Holden was too smart for his age, too philosophically aware of what life was really about for a boy of 16.
When other kids his age are acting carefree and not paying attention to important subjects like death, Holden is trapped in unresolved grief trying to understand the death of his little brother within the larger question of what is life about anyway?