There have been modern kids authors that focus on boys: Darren Shan's vampire series, Anthony Horowitz's Alex Rider books, Rick Riordan, the Artemis Fowl series

There have been modern kids authors that focus on boys: Darren Shan's vampire series, Anthony Horowitz's Alex Rider books, Rick Riordan, the Artemis Fowl series, etc. Jon Scieszka did his Time Warp Trio books for example. Dav Pilkey did Captain Underpants and various other series. There's the Diary of a Wimpy Kid series, and more. However, the massive bulk of the market ends up being targeted towards women. It's something where you'd need to actually look on shelves for, as there's a weird dynamic where in female-dominated markets or places, you have male "figurehead" things while the rest of the market is dominated by and caters to women. I noticed this in Christian fiction ironically. You will see a big author like Ted Dekker doing his spiritual action adventure/fantasy/mild horror for a wide audience, but the huge bulk of the books are historical/amish/mystery romance aimed at women, to the point where no male alternatives exist. Even the small religious science fiction market is female dominated soft romantic sf. In this case it's milking established demographics, as the religion itself has a mild demographics issue (not enough men.) But go look at a young adult shelf sometime; even superhero books feature women protagonists and are targeted to them now.