Attention Star Wars fans -- a little help, please

Does he like to read, do the books have themes he'd be invested in? (haven't read them)

On one hand, a <2 hour long movie to show a cool character, vs reading three books is just not equal, I think the show can make one more interested in the legendary stories of the smuggler.
On the other hand, I read the Hunger Games books without watching any of the movies, because the story itself was interesting, so here's an example of an interesting book being convincing enough to get into them.

So the question is, if he's more open to the idea of building up a character, and then having him in the movies as a main-side (?) character, or want to show Solo as a mysterious character with shady past in the movie, who can be explored through the books.

Most of the time I'd say start with books, esp if they're the original source of the series (Lord of the Rings is possibly an exception). But I have to admit with things like Star Wars or other significant cultural works I feel that starting with the OG trilogy is the best way. The character of Han Solo is, imo, inexorably and forever linked to the depiction in EPs 4-6 and the performance of Harrison Ford in particular.

(Don't get me wrong, Solo is....... an ok film, not up there with the best but it's not a bad way to spend a couple of hours. But it is terminally crippled by having to somehow replicate the whole body of OG Han Solo built up over 30+ years. The actor was serviceable and in a world where the OG trilogy never happened, or at least not with HF then he could have possibly crafted his own cultural moment. But the shadow of HFs Han stood too tall to overcome, especially with a fanbase that wasn't entirely willing to go part way).

So much of the nuances that filter through into other media can only be appreciated after knowing the originating material. (Indeed, this is where I feel the in-universe chronological order for SW advocated by many falls down a bit, I would never start the journey of Han Solo by actually showing his origin movie first and I would even go as far to say the movie is not designed for anyone other than people who have seen the OG trilogy). Han is one of those rare things for sci-fi, a truly culturally iconic character that I feel is almost entirely dependent on the OG depiction. Every other depiction, whether in print or games or other media ultimately feeds off and leads back to that original depiction.

Tl;dr in the case of SW the OG trilogy I feel is the ultimate starting point for appreciation of the character. Just as you wouldn't introduce Indiana Jones, Doctor Who or Captain Kirk by giving people novelizations or side media first, the true foundation is that particular performance over those 3 movies.

definitely not the books as a start, since movies are much more digestible. Depending on his age and his available platforms and interests he might enjoy Lego Star Wars: The Complete Saga.

The best advice is usually to start with what was coming first. In this case the movies.

I think these things should be done in publishing chronological order. Any prequel will give you info from the original movie, if you watch the prequel first and the original movie later, you'll have too many hints of what will happen, or how characters are and where they come from. It should be discovered in the reverse way. Like ok, here you've had this awesome character, now we're going to have a long flashback to know how he became the way he's now.
This is the same situation, I think. While e.g. the Solo movie didn't tell much of SWIV, it tells a lot of how Solo became Solo, and how much he was already cocky, arrogant, and the best pilot of the galaxy, not to say how he met his loyal companion Chewy or Lando himself.

So, I'd make him watch the whole 4-6 original trilogy (sorry for the cringy ending of RotJ), and then throw at him anything SW you think it's important, entertaining or interesting.

Thanks, all. I recommended to him that he watch SWIV before reading.

What age? If a young reader, I'd recommend the junior novelizations of the first 3 movies and the Jedi Apprentice book series. They're based on the prequel trilogy (Phantom Menace, etc).

https://starwars.fandom.com/wiki/Star_Wars:_Episode_I_The_PhantomMenace(junior_novelization)

It has a hardcover https://www.ebay.com/itm/155759704205

https://starwars.fandom.com/wiki/Star_Wars:_Jedi_Apprentice

Film (the original trilogy) first, then books.

I'm pretty sure the books might spoil the movies quite a bit and even with Solo being a prequel, they might have used elements from the books in there so I agree with the general consensus.

How lucky your nephew is. I wish I had the whole of Star Wars to experience all over again!
I can't wait to buy more grown-up books for my nephew. Don't get me wrong he loved every book I ever gifted him and it's cool to talk about Captain Nemo and Greek Mythology and all... but Star Wars... can't wait!

Nothing quite like being the cool uncle/aunt/third option, is there? ;)