Music Reading for Guitar byDavid Oakes

The ability to Pick up a piece of sheet music for a song I have never heard before and instantly play it on  guitar by reading the sheet music. That's what I think the definition of sight reading is.  I can't do that but I want to be able to do it.  I know what the notes are in the treble cleff anyway but can't figure out the rhythm of the notes or figure our the best position for my left hand.  I am thinking about buying the book Music Reading for Guitar by David Oakes to help me acccomplish that goal.  Has anybody bought that book and tried it out?  If so,  what did you think of it?  Any other suggestions in learning how to sight read?