While I would not argue for "The Family Tree" being Tepper's most engrossing book, it must surely count as one of her most ambitious to date - if, that is, one measures such things in terms of complexity of plot, departure from comfortable suppositions and desire to undermine and overthrow most readers' pre-conceived ideas and assumptions! Sheri S. Tepper is, of course, a past master (I should perhaps rather say, mistress!) of such matters and she handles it here with consummate ease. I don't believe that anyone could make it to the end of this work without finding themselves both surprised and shocked at some stage of the journey. I also found that a deep personal re-evaluation was needed by the end too: something else that Tepper is always supreme at provoking. The book does perhaps require a little more effort than most of Tepper's other works (except, perhaps, "The Revenants"): mostly, I think, because of the greatly disparate nature of the two parallel story threads and lack of obvious connections between them. Also, I think that Tepper deliberately prevents the reader from acquiring too comfortable a toe-hold in either world, purposefully allowing one to assemble an entirely false set of assumptions about where, when and who... only to have her take great delight at demolishing those assumptions, time and time again.
Unfortunately, I think that the price that gets paid this time is that she also fails to make either world (or their coming together) entirely believable. If you're prepare to suspend disbelief, though...
My only complaint of this book is that there are some intriguing plot elements which felt never to come to anything - just why does she go to such lengths to ensure that Opalears is dressed as a boy, for example? But then, so much of this book comes to so much more than one is expecting that I'm perfectly happy to accept these as smoke screens! Or even to accept that I missed their resolution in the cataclysmic happens that occur around them.
Yes, Ms Tepper has done it again!