There are many ways to improve sight-reading - Czerny 599 is not a bad way, but it depends on how you use it.
You'll find that exercises are grouped - so a concept will be introduced, and the next few etudes are just variations on that concept. e.g. if you play no. 11, you'll then discover the LH notes stay the same for the next six or so etudes. So you should have no trouble recognising that pattern.
Because my teacher didn't want me to memorise letternames of the notes, and only know how to play in C Major, I was required to transpose these into various keys - that way, I learnt to recognise the intervals and the "shape" of the chord - i.e the way a chord looks on the page, and that corresponds directly in my mind to the correct inversion etc.
This is why Czerny 599 is good - it's so simple, you can do this to the entire 100 and it won't take you that long. Of course, you might not want to transpose the later ones which have key signatures of many sharps!!!