1. Nobody Lives Forever - it's a terrific story and just motors along very happily; the singlemost purely entertaining Bond novel by any author.
2. Colonel Sun - if you're looking for something more closely associated with the source novels, not just in timeframe but also style.
3. Scorpius - stunningly violent in places, possibly the most violence of any Bond; some very interesting, prescient ideas.
4. Hurricane Gold - oddly affecting, melancholy characterisation, amidst some amusingly peverse ideas. Cracking.
5. Blood Fever - tremedously exciting, funny, an absolute blast.
6. Role of Honour - veers towards the dry but, again, some fun notions popping up.
7. For Special Services - if you're looking for a bit of a hoot; bit daft, really, but maintains interest.
I struggle a bit after this
8. Icebreaker - if you're looking to be confused: much of it is very enjoyable and the setting is unusual but it is horrendously contrived.
9. Licence Renewed - OK, but it takes an awfully long time to get going and the details overload at the expense of the story.
10. Devil May Care - some of the ideas are huge fun but the execution of them is very dodgy: unnecessarily drawn out towards the end.
I would be cautious about anything Gardner from 1990 inclusive as he appears to be writing about Captain Boldman, a different and much more stodgy character, and the Bensons aren't happy experiences, save perhaps DoubleShot. Carte Blanche is better read as a Dan Brownesque pastiche than (ahem) seriously as a Bond book.
Obviously I would advise reading them all, so far as time and budget allow. The Higsons are perhaps the most consistent in quality. If you can get hold of the Christopher Wood novelisations, they're very, very good but (if only to cover up the wretchedly shaming fact that I forgot about them in listing my top ten above) I wouldn't consider them "continuations" per se.