I have others, but guess I have to wait for future days to post them. (What's the point of that, exactly? Seems more irritating than anything else. Also, more likely to dissuade participation -shortening your lists- as people just don't return, forget, and/or have other things to do [irl] besides returning just to type out one item, than it would lengthen your threads/responses.)
I was being pessimistic and thinking some folks would just come in and dump 50 without comment. Was hoping for just the top few, wanted everyone (well, lots of people) to have the chance to add something new to the list, and was hoping it would encourage some commentary.
A lot of people consider The Sword of Shannara to be derivative of Tolkien's The Fellowship of the Ring. (I'm not sure why Sword gets singled out while other, even more derivative works get a pass, but anyway.) I feel like once that reputation was established, readers began to apply it to all of Terry Brooks' works.
Whether you believe the critics or not, you'll find that The Heritage of Shannara series is less derivative than the first trilogy. The setting is the same, but the plot, the tone, and the character arcs are more modern and Brooks manages to avoid many (but not all, alas) of the bad fantasy tropes that are prevalent in the genre.
Another big difference is that Heritage is much more representative. In The Sword of Shannara, there is only one female character (Shirl), and she has a very minor presence in the story...essentially she exists solely for another major character to rescue (by accident, I might add) and fall in love with. That old "woman as a quest reward" trope is everywhere in the whole fantasy fiction genre, and The Sword of Shannara is hardly the worst offender, but it's a solid criticism.
In contrast, Heritage has numerous female characters that are essential for driving the plot (Wren Ohmsford, Quickening, Damson Rae...), and they are much better written. There's at least one black main character (Walker Boh, the titular "Druid of Shannara" of book 2) as well. It's not a perfect book series; there's a heavy-handed "doomed romance" arc that today's readers might roll their eyes at, but it's still much better than the terrible "broken bird" trope in Elfstones of Shannara (the second book of the previous Sword of Shannara trilogy.)
Can't remember the exact title, but we had a book of "weapons and armours through the centuries" (or something like that) when I was a kid. So not exactly a novel or even fiction, but it was one of my earliest important inspiration and foundation of my love for things medieval. Later there were bandes-dessinées (Belgian-school of "comics") such as Thorgal that cemented that interest, or even Johan and Pirloui (and the smurfs). And then the classic novels proper (LotR series et al)
For my kids and their friends however, the question is more like : "what one book/series were you inspired to read because of D&D?"
I'll do two, one I'm reading now and another I read as a child.
Journey to the West is a really great example of world-building, making an adventuring party, a clearly defined goal (go to the West to deliver some scrolls!) that is continually derailed by fun and thrilling side-quests. It's a great reminder that not every adventure needs to have doom-and-gloom, world-ending or even city-ending stakes... all you got to do is walk across a continent! Filled with memorable encounters, some solved through combat but many others with trickery and diplomacy, there's a lot to learn here and it's a great read (if you like reading truly old-school poetry-novels!). If you need a Western equivalent, pick up the Odyssey, they got a similar shtick!
And childhood book, Eragon. Yeah, it's essentially the plot of Star Wars in Tolkien-world (with a dragon), but who cares we all love it! The latter books get into more developed themes and character arcs, but this first book was a big hit for a reason... it's got the heroes journey nailed down pat, with another world-building trek across the continent.
For me I find the books most inspriring. My wife made the observation that I am literally better at understanding story through books than movie or TV. I miss so much when I watch movies or TV, I get looped in technicalities.
Several books from Andre Norton comes to mind. Inspirational in terms of lots of interesting antagonists, characters, and worlds. She was a prolific, pretty awesome author.
A perennial favorite is the Witch Worldcycle. For an story based on an actual D&D session with Gygax, check out Quag Keep. For a very cool take on an other-world faerie world, check out Dread Companion.