I made an extensive review of the 11th edition, which I still own, and so I'm able to make a comparison between the two. In fact, I've owned editions over the years stretching back to the 6th edition, so I'm practically married to this atlas (in addition to owning several other old standbys).
First I'd like to express my dismay about how reviewers of the 13th edition got distracted by the mindless AGW debate. (There should be no debate: AGW is real.) This debate is so emotional it seems to cause rational judgment to take flight completely and for people to get totally side-tracked from issues relevant to the topic at hand. It's absurd that the judgment of the rating of the 13th edition would be so negatively biased. This edition is at least as good as any previous edition, and should average five stars, just as all the other editions have over the last few decades.
It's utterly pointless to debate about whether this is the best commercially available atlas. So I'm not going to rehash those ancient arguments. Rather I'll point out the differences between the 11th edition and this 13th, and let those with the 11th decide whether the differences merit the purchase of this new edition.
I compared them page by page, and to my astonishment, the choice of maps and coloration are virtually identical, page per page. There are only two differences in the maps that are actually chosen. They have thankfully restored the full plate of Alaska found in editions earlier than the 11th (there, sorely missed), at the expense of eliminating the 1:2,750,000 map of Chile central and Argentina central. For North Americans, this is a much welcome tradeoff.
Another improvement in the 13th is that the ocean maps now show color-coded elevations on the neighboring continents. The 11th editions showed monochrome continental margins on the ocean maps.
A minor improvement is the font used in the title of each page. The 11th and previous editions used too bold a font. The new uses a thinner lighter, and less distracting font, more in tune with modern typographic standards.
My main concern before receiving this edition was the decrease in price and weight over previous editions. What was sacrificed, I was wondering? The weight difference stems from slightly thinner sheets and a slightly less luxurious cover. The 11th is 1.625 inches thick and the 13th is 1.5 inches thick, a difference of a mere 1/8". The cover is less robust in the 13th. It is cardboard, whereas the the 11th is cloth. The 11th also has a dust cover and the 13th does not. The dust cover is actually somewhat of a nuisance (just one more thing you have to be careful with), but it does give it a flavor of luxury.
Most notable is that the 13th lies flatter than the 11th. In fact the 11th was characterized with having the kind of binding that does *not* lie flat. The 13th is more like versions previous to the 11th, in lying flatter.
A really welcome improvement as far as I'm concerned is the finish on the paper plates. Previous editions had a matte finish with a higher coefficient of friction than the semi-glossy, silky smooth finish of the 13th edition. I really like the finish of the new plates: they feel utterly luxurious and sensuous. So I wouldn't fret about the slight loss in weight and thickness of this 13th edition. But the new paper is just a tad less robust than previous editions. The pages are so large it is easy to impart tiny creases in the pages if you aren't careful turning them.
When I reviewed the 11th edition, I did it under standard incandescent lighting, and complained about the "busyness" of the maps, due to how "tiny" some of the fonts were, and how dense the labeling sometimes was in densely populated areas. Now it is much more widely known that full spectrum lighting vastly improves the readability of small fonts, and I've now used full spectrum lighting in my reading lamps for five years or so. I use a bright (70W) full spectrum (5900K & 96 CRI) fluorescent lamp behind my shoulder pointed down on the atlas. The difference from incandescent lighting is astonishing, and I am no longer bothered by the "business" of the Times Atlas labeling.
I now find myself with little incentive to keep my previous edition. I kept my previous edition of the 11th simply because it had that map of Alaska. It has now been restored. One less book to clutter my book shelves. I've reached the age (70) where massive downsizing is in order anyhow.