What one book would you give Reagan, Bush, Mondale, Ferraro?

This is an invitation to help us prepare four clearly needed lists of gift books - one for each of America's major national candidates: Republicans Ronald Reagan and George Bush and Democrats Walter Mondale and Geraldine Ferraro.

It is fine to ask what books candidates have read, as the debate pundits do, and as Nicholas A. Osgan of New York did so succinctly in a letter to the New York Times last month: ''What do I care about Geraldine Ferraro's or any other candidate's income tax returns? How about a list of books they have read recently?''

But who could not suggest some one appropriate book, old or new, that each candidate should read before it is too late? - that is, in order to possess a rounded outlook on the next four years? Presumably it would not be the same book for Mr. Reagan as for, say, Mrs. Ferraro.

The Home Forum proposes to publish by Election Day the candidates' gift book lists chosen from your suggestions received by Oct. 12. Please send no explanations, and no more than one title (with author) per nominee, specifying Reagan, Mondale, Bush, or Ferraro. Omit religious books, which will be left to the candidates' own choice. Address: The Home Forum (Candidates), The Christian Science Monitor, One Norway Street, Boston, Mass. 02115.