Basically they've brought together every known illustration, map, or rough sketch Tolkien made for THE HOBBIT,* arranged them into order of where they fit into the story, and added a page or so describing each piece or set of closely related pieces. One particularly nice feature is that they've been able to use multiple gatefolds to bring together sequences, where Tolkien went through a series of attempts to capture a particular scene, like The Hill at Hobbiton, or the Elvenking's Gate, or Smaug flying 'round the Mountain.
I did my best to demonstrate the importance of Tolkien's art to the story in THE HISTORY OF THE HOBBIT, but there I only had twelve plates and two frontispieces to convey what they've used 144 pages to get across. And it's wonderful to see (particularly for those of failing eyesight, like myself -- the community of Tolkien fans and scholars alike being an aging one) the pieces are, as Wayne & Christina point out, "reproduced . . . as large as possible" [p.17], rather than shrunk down (as I needed to do to 'stuff every rift with ore', as Jn Keats wd put it). It helps that this is an oversize square-format book (ten & a half by ten & a half inches) in a handsome slipcase, resembling the original edition of PICTURES BY TOLKIEN more than it does ARTIST & ILLUSTRATOR.
The results are, I repeat, wonderful. Tolkien didn't have much confidence in himself as an artist, but like Thurber and Lofting (fellow artistic autodidacts) his work is distinctive and instantly recognizable; it's part of the tales.
And this is a definitive collection: there are a few pictures here even I've not seen before -- for example, the more detailed picture of Elrond's house [#18], or the rough sketch of Eagles' Eyrie [#40], or the first version of The Three Trolls Are Turned To Stone [#14] (I find I prefer the trolls' faces here to the final version). And many more here reproduced in sharper detail than ever before -- e.g., all the dwarven activity at The Back Door [#69]. Others I've seen at some point but not paid much attention to; here they stand out much more when placed in the right context (like #35: The Misty Mountains, which had previously been tucked at the end of the index of ARTIST & ILLUSTRATOR [H-S#200]).
This book is relatively text-light, compared with ARTIST & ILLUSTRATOR, which is as it shd be: here the focus shd all be on presenting Tolkien's art as clearly as possible. Their introduction does a good job of covering a great deal of territory in relatively little space: only eighteen pages to discuss the origins to the book, explain how the art came to be created, and comment on the "rich visual experience" of the results. I particularly admired the economy with which they addressed various complex and thorny issues -- as, for example, dating when Tolkien began and finished the story:
". . . around 1930 (the evidence is too contradictory to give a precise date), [Tolkien] began to write [The Hobbit]" [p.9]
". . . It may have reached substantially its published form by the time Tolkien lent it to C. S. Lewis around the start of 1933, or it may be that its final chapters . . . were not composed until Allen & Unwin showed an interest in the work in 1936" [p. 10]
--While I think the 1930 date is pretty firm, that's a great way of getting a lot of information judiciously into v. little space (even the choice of the word write is significant, given speculation about oral tales); likewise, they acknowledge but do not take a position re. the Carpenter hiatus. Anyone who's delved into the complexity of the evidence re. these two points can appreciate how difficult it is to clearly explain them without oversimplification: here I think there's just the right amount of simplification for this context (where the emphasis is, and shd be, all on the art).
Finally, I'm envious of one thing. They've pulled off something I wanted to do in RETURN TO BAG-END but in the end wasn't able to: assemble all eight known pictures of Bilbo** onto one spread. In my case, I simply ran out of space, and in the end agreed w. my editor at HarperCollins that it'd be better to include two more new pieces rather than devote a page to reproduction of pieces already appearing elsewhere in the book, esp. given how small the eight pieces wd have to be to all fit onto one (nine-inch by six-inch) plate. Freed of that restriction, Wayne & Christina reproduce enlargements of them all. Looking at these side-by-side is illuminating: it's clear that Tolkien had a v. clear image of what Bilbo looked like; despite his difficulty with drawing faces there's a recognizable likeness in BB's features in the majority of the portraits. It's also interesting to note that Bilbo wears some sort of footwear in four of the eight pictures (Tolkien having meant to insert a passage re. Bilbo's getting shod at Rivendell before heading up into the mountains but never having gotten around to doing so). Well done!
*with the possible exception of the tracings of the two hasty sketches of Gandalf's hat that appear in the end of the new one-volume H.o.H. [p.901]
**at the doorstep of Bag End, inside Bag-End smoking, in the bushes by the trolls, barrel-riding (two images from different versions of this scene), bowing to Smaug (in silhouette), resting in the Eyrie, and in the sketch he drew for Houghton Mifflin, this last having first been reproduced in H.o.H.).