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Im thinking you may get this a lot and here is why I think the Mario socks are the best choice on the list. It sounded like your brother is into things that can be nostalgic. So of the current list I'd say those.
If you don't mind the cost. I recommend thisamazon
Well, there's Transformers: A visual history by Jim Sorensen that's absolutely fantastic, it goes into the complete detailed history of the Transformers and is a pretty comprehensive reference to everything related to Transformers.
If that's not what you're looking for, I also really enjoyed Transformers, Vol. 6: War's End which chronicles the war for Cybertron. I have to be honest though that it will make more sense if you first read volumes 1 through 4 as well as Fate of Cybertron. Hope this helps!
Transformers: A Visual History https://www.amazon.com/dp/1974710580/ref=cm_sw_r_cp_api_glt_fabc_YAV9KMQTA6FZDF7PZA3Y
I got you, good luck