Tom Startup pointed out that flammable and inflammable appear to be opposites but actually mean the same. Someone called Generally Right offered slim chance and fat chance, which is nice. Adam Huntley offered passive and impassive, although they are not quite synonyms.
1. Habitable, inhabitable Nominated by Chris Jones and Graham Kirby.
2. Heritable, inheritable Chris Jones at the double.
3. Press, depress From Jon Baines and Martyn P Jackson.
4. Bone, debone Jackson again, along with Richard Sagar, CazzPink and Graham Kirby.
5. Valuable, invaluable Nominated by Jon Baines and Graham Kirby.
6. Bar, debar From Stacey Murray. The Oxford English Dictionary says debar is from the French débarrer, itself from the Old French desbarrer, unbar.
7. Personate, impersonate From Carl Gardner, who reminds us that "personation" is the term for an electoral offence.
8. Ravel, unravel Xlibris1 again and Francis Wheen, who says: "My beloved Chambers dictionary app gives 'unravel' as a definition of 'ravel'."
9. Privation, deprivation Suggested by Xlibris1.
10. Genius, ingenious An ingenious one suggested by both Graham Kirby and Fiona Wright.
Next week: Fictional countries (not including 'the UK')
Coming soon: Books narrated by a killer (guest list by Peter Swanson). Send your suggestions, and ideas for future Top 10s, to firstname.lastname@example.org.