In reply to paul29uk:
I don't take the Ground Up guide with me as it would not stand up to the wear and tear that I would give it.I do however peer through it for ideas and bedtime reading.
You could also look at the old and out of date Paul Williams Snowdonia guide.I still use that partly as it covers a wider area and also there is the sense of history with it.(It does not have the best of indices, and the topographical photos are black and white and not the best).
If I were you I would buy the CC Llanberris guide and the Ogwen one, as those are the areas I would go to when first going to Snowdonia and they are superb.Later you could add Tremadog for when the weather was not so good in the pass and environs.Then you could add Gogarth North for a peer at Holyhead Mountain and the sea cliffs, and Cloggy for when the weather is stable.
Rob