Couple of unusual ones.
The Death of Grass - John Christopher
A little bit Day of the Triffids. But also very good indeed. Looks at the consequences to society of a disease whch destroys all the grass family, including wheat, rye, and rice. Worldwide.
When Gravity Fails - George Alec Effinger
I was overjoyed to see this title has been reprinted recently, with blurb on the cover to indicate it is finally getting the recognition it deserves. GAE is one of the best sci-fi writers I've ever read, for the humanity of his characetrs, and the the (admittedly intermittent) originality of his ideas and settings. When Gravity Fails is the first in the Budayeen trilogy, which terminated with the author's death from cancer. And in many ways it echoes the desperate energy, despair and hope one finds in late work by Bill Hicks.