Being relevant to the public is very different from being relevant to historians. While you and I may never even think of it, Gen. Grant's autobiography is still part of debates about Grant, Native affairs, slavery and reconstruction, etc. The same can be said of almost any book, even the classics. Classic fiction is usually not discussed by the general public, but academia happily discusses it.
Anyway, if you would like discussions to continue, check out some academic journals and go to events where papers are discussed. You'll find them being discussed there.
Biographies are a different issue and for them it depends on how close to the source both in time and location the book was written.
Now I'm missing all my lovely college days. God, history is amazing.
Well, that's sort of true. As documents, political memoirs are useful up to a point. Historians do read these tombs to get a sense of the age, how the person likes to present themself, and as a mine for tidbits of evidence. But they're rarely the subject of historiographic debate or controversy in and of themselves. As a professional historian myself, I tend to use memoirs more to corroborate a point I've pieced together from primary/archival material, rather than as the thrust/basis of the argument.
