I haven't read any of the books you've listed, so I don't know how these will mesh with your son's tastes, but I agree with zelda_zee's suggestions (the second Rothfuss book is out, but only in hardcover at the moment - the paperback comes out in March, I think).
And then I would add Scott Lynch's Gentlemen Bastard series. Only the first two books (of a proposed seven, I think) are out now: The Lies of Locke Lamora and Red Seas Under Red Skies, and they are so, so good. They're quite long, and yeah. Really good.
Um, Sherwood Smith has an actually completed series, the Inda books, that I liked a lot. (Inda, The Fox, King's Shield, and Treason's Shore. And Tad Williams has a few series, and is generally good.
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And then I would add Scott Lynch's Gentlemen Bastard series. Only the first two books (of a proposed seven, I think) are out now: The Lies of Locke Lamora and Red Seas Under Red Skies, and they are so, so good. They're quite long, and yeah. Really good.
Um, Sherwood Smith has an actually completed series, the Inda books, that I liked a lot. (Inda, The Fox, King's Shield, and Treason's Shore. And Tad Williams has a few series, and is generally good.