The Cat Who Walks Through Walls (1985)

From Publishers Weekly
As the old guard of SF ages, we are getting more novels of nostalgia. Heinlein is less sentimental than many of his generation but his new book resembles both the latest Bradbury, in making the author the protagonist, and the latest Asimov, in returning to a popular series from early in his career (Future History). Like Heinlein, Richard Ames is an ex-military man turned writer who fancies himself a pundit. An assassination attempt precipitates his marriage to Gwen Novak and sends the newlyweds scurrying to the Moon and then to the planet Tertius, headquarters of the Time Corps. The action, though, is largely beside the point in a novel that is predominantly a dialogue between the protagonists. Their foredoomed attempt to become the Nick and Nora Charles of space (with a bonsai standing in for Asta) is sabotaged less by Heinlein's endless elbow-in-the-ribs wisecracks and more by his inability to convincingly portray a sexual relationship. Given the increasing popularity of his recent, similar work, it is unlikely that the book's short-comings will limit its potentially large audience. November 11
Copyright 1985 Reed Business Information, Inc.
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From the back:
IN The Cat Who Walks Through Walls, he creates his most compelling character ever: Dr Richard Ames, ex-military man, sometime writer and unfortunate victim of mistaken identity.
When a stranger attempting to deliver a cryptic message is shot dead at his dinner table, Ames is thrown head first into danger, intrigue, and other dimensions where Lazarus long still thrives, where Jubal Harshaw lives surrounded by beautiful women, and where a daring plot to rescue the sentient computer called Mike can change the direction of all human history.