Your description made me think of 'Oh, The Places You'll Go' by Dr. Seuss for some reason. Not called 'The Thing' but definitely a book to end all books depending on who ya ask.

Okay, this is a shot in the dark, but maybe 'Things Fall Apart' by Chinua Achebe? It's a classic, and while not exactly 'deep stuff' in the philosophical sense, it's got layers. And there are a ton of cover designs out there.

The vagueness is challenging. However, 'The Thing About Life is That One Day You'll Be Dead' by David Shields might fit. It uses a combination of personal narrative and scientific fact to explore life. Also possible to find editions with either red or blue covers.

lol, it's totally 'The Hungry Caterpillar'. Deeeep stuff in that masterpiece, changed my life. But for real, maybe give us more than 'thing' and 'stuff'? 😂

When you say deep, are we talking philosophy deep? 'The Thing Itself' by Adam Roberts springs to mind. It's all about using Kant's ideas in a sci-fi setting, pretty mind-bending stuff but a long shot from your description.

idk if this helps but there's that book 'The Everything Store' by Brad Stone abt Amazon? Prob not it but hey, it has 'thing' in it 🙂

hmm 'The Thing' sounds familiar, there's a 'Swan Thing' or something by John Green, maybe? idk covers change so could be red or blue, right?

Could it be 'The Important Thing' by Margaret Wise Brown? Sounds kinda like what you're describing, it says profound stuff in simple words and might have had different cover editions.