[The Squatter of Amon Rûdh]

"The names Sauron and Saruman are too similar. I believe many people have read through much of the book thinking they were the same person."

Possibly, but it would have to be a very cursory reading, with many breaks to do other things. They are very similar names, though. Perhaps this was even intentional and the characters are parallels: Saruman does appear to me as a sort of petty Sauron, perhaps even acting as a hint at the manner of the Dark Lord's own fall from grace. Certainly he appears to be a putative Dark Lord, best removed while he's still building his power-base.

JRRT was, as he said, the most critical reader of all. No perfectionist is ever entirely happy with their own work.