Although good old-fashioned storytelling makes this book a success on its own merits, it is also a fine melding of the events of its predecessors, Racso and the Rats of NIMH (1986) and O'Brien's Newbery-winning Mrs. Frisby and the Rats of NIMH (1971). Sullen junk. food- and TV-addict Margaret is forced to go on a family camping trip, during which she becomes lost in the wilderness with her silent little brother Arthur (R-T). They encounter Christopher, one of the rats from the NIMH colony (superintelligent laboratory rats who escaped to paradisical Thorn Valley). Their involvement with the rats alters Margaret's and Arthur's lives while setting into motion the end of the NIMH colony as most readers know it. Witty characters, both rat and human, fill out an adventure-packed plot of both minute and grand proportions. Margaret's transformation is sweetly complicated; her growing tolerance for her brother's ""strangeness"" is an excursion in maturity. It's possible to enjoy this without the context or continuity provided by the other two books; but the uninitiated will surely waist to seek them out. Lubin's delicately detailed b&w art makes the format as attractive as the text.