I’m writing this current manuscript in first person, present tense (I walk). I’ve never written the majority of a novel in present tense before—although the hospital scenes in Red Audrey are in present tense—and for the scholars among you, there’s a dirty tense trick in the last hospital scene.
The weirdest, and most fascinating of my grad school professors railed against present tense as a dangerous fad. He argued that past tense is designed for writing: “Jim biked up the hill. He was biking slowly. He had biked earlier and injured his leg. He had been biking on an injured leg for weeks.” And that readers have learned to recognize shifts in past tense to indicate flashbacks and time shifts. He felt that present tense required distracting tense constructions to indicate time shifts. “I bike up the hill. I am biking slowly. I have biked earlier and injured my leg. I have been biking on an injured leg for weeks.”
Over a page, a chapter, a book, the difference might be more remarkable, but I do think that in present tense, I have to be more conscious about shifting into a past episode so that the reader realizes we’re in the past, and doesn’t read past tense as the present experience of the book out of reader-habit. (Also, I avoid present perfect—“I have biked earlier and injured my leg”—because it’s too jarring, and sounds ugly.)