Google are continually adding to their library of out of print books that they are making available on-line. Whilst some are, frustratingly, not available in the UK because of copyright issues, many are.
I have recently been referred to Debrett's The baronetage of England for a particular reference, but by entering 'Douglas' in the search box, I was able to call up many interesting references.
Try this link>>>
Early Debrett's are notorious for the mistakes, and indeed many entries are still not fully accurate, so, as always, check your facts!