If you want to get into the Marvel comic book universe I think those box sets are overkill. Each of those series are fewer than 10 issues, but the box set is filled out with tie-in comics from monthly titles that were being published in parallel with the mini series.

As a reader new to comics I'd recommend starting with the 6-10 issue main miniseries. It'll be a lot cheaper and provide you with the main storyline. If you absolutely fall in love with one of them then maybe splurge on the box set to get a fuller context around that main storyline.

For getting into Marvel comics in general, and with your affection for hardcovers, I'd recommend Omnibus volumes of the most acclaimed runs.

John Byrne's Fantastic Four
https://www.amazon.com/Fantastic-Four-John-Byrne-Omnibus/dp/0785158243

Chris Claremont's Uncanny X-Men
https://www.amazon.com/Uncanny-X-Men-Omnibus-Vol-Marvel/dp/1302900838

Stan Lee's Amazing Spider-Man
https://www.amazon.com/Amazing-Spider-Man-Omnibus-Vol/dp/130290082X

Ed Brubaker's Captain America
https://www.amazon.com/Captain-America-Omnibus-Vol-1/dp/0785128662

Walt Simonson's Thor
https://www.amazon.com/Thor-Walter-Simonson-Omnibus/dp/0785146334

The other series you mention, Sandman and The Walking Dead are great examples of comics that succeed outside of the typical Superhero motif. They're both fantastic, but will be quite different from any of the examples above.

EDIT:
I should mention, if you're OK going digital, Marvel Unlimited is a very nice subscription service that provides access to a large portion of their 70+ years of content. It works great on a tablet, but I wouldn't recommend it on a phone or PC.