He was reading a copy of Aldous Huxley's The Doors of Perception – a 1954 essay about the writer's experiences tripping on mescaline. No doubt the counterculture icon Huxley was an inspiration for Lee when he created the equally trippy Doctor Strange back in 1963.
Given that his cameos are usually short and quick, we wouldn’t count on it.
IN RESPONSE TO THE COMMENT
I picked this up from Wikipedia
Artist Steve Ditko and writer Stan Lee have described the character as having been originally the idea of Ditko, who wrote in 2008, "On my own, I brought in to Lee a five-page, penciled story with a page/panel script of my idea of a new, different kind of character for variety in Marvel Comics. My character wound up being named Dr. Strange because he would appear in Strange Tales."3 In a 1963 letter to Jerry Bails, Lee called the character Ditko's idea, saying,
Well, we have a new character in the works for Strange Tales (just a 5-page filler named Dr. Strange) Steve Ditko is gonna draw him. It has sort of a black magic theme. The first story is nothing great, but perhaps we can make something of him-- 'twas Steve's idea and I figured we'd give it a chance, although again, we had to rush the first one too much. Little sidelight: Originally decided to call him Mr. Strange, but thought the "Mr." bit too similar to Mr. Fantastic -- now, however, I remember we had a villain called Dr. Strange just recently in one of our mags, hope it won't be too confusing!