Shelly's book is 535 pages long. She has read 175 pages so far. If Shelly reads 90 pages per day, how many more days will it take her to finish the book?

Shelly has read 175 pages so far and needs to read 535 pages total, so she needs to read 535 - 175 = <<535-175=360>>360 more pages.

If Shelly reads 90 pages per day, it will take her 360 / 90 = <<360/90=4>>4 more days to finish the book. Answer: \boxed{4}.