Hello, JohnnyT!
the book (the 12th planet) stated that Venus (I think) is further away from the Sun than Earth, but it is actually a much hotter planet.
They lied, or you misremembered.
Venus is farther from the Sun than Mercury, and its surface temperature may be a bit hotter. That's because Venus has a very thick atmosphere, and Mercury has essentially none.
There isn't a twelth planet. Or 11th, or 10th. Sorry.