Has Concerns About Revising Another Author's Book

Dear Rich: I was recently asked to revise a book that another author wrote. The publisher claims ownership of the original writer's book. Before signing on, would I not need to request access to the original contract between the publisher and original author; to ensure there isn't some way the original owner could take back their ownership rights (and myself out any financial gains from my work)? I am thinking there could be some clause to rescind ownership (don't know) but what makes me uneasy is the publisher has a very aggressive schedule for wanting this revision and I can't understand the urgency.

It would be fairly reckless for the publisher to contract for a revision knowing it lacked the rights to modify and republish the book. If you're concerned that the publisher is not being truthful, you should avoid the arrangement or consider using contractual clauses known as warranties and indemnity in which the publisher "insures" you against the disasters you describe. (We've talked about these provisions here and here).
What about the copyright? You could consider researching Copyright Office records. Of course, determining copyright ownership may not always answer your question as some authors exclusively license book rights to a publisher but keep the copyright. Or alternatively, a publisher may have held the copyright but rights reverted to the author typically if the book were out of print.
Trade custom. In any case, publishers routinely contract with outside authors to revise books in their catalog and typically the underlying author agreement is not provided. That could be because of confidentiality reasons, or because the publisher may not wish to reveal the terms of the author agreement to a third party, or the publisher feels it has no obligation to do so. As for the publisher's sense of urgency, it could just be business as usual.
P.S. Is the original author of the book available to answer your questions?