for drinking glasses only, Bickerton is probably the best low budget volume - 'C18 English Drinking Glasses' - although his coverage is of British only - beyond that, some of the specialist books which include Continental material do become rather pricey.
For general collectable glass which includes the C18 and early C19...........
'Glass Through the Ages' - E. Barrington Haynes (paperback)
'English & Irish Glass' - Geoffrey Wills
'Irish Glass' - Phelps Warren - but make sure you get the completely revised 1981 book, and not the ealier volume.
'Investing in Georgian Glass' - Ward Lloyd.
'British Glass 1800 - 1914' - Charles Hajdamach.
should be enough to be getting on with. Of course, other people may have their favourites - so they may like to share their suggestions with us