"Girl" books that boys love
Hey, so you've noticed that girls will read anything, but boys often refuse to read a book about a girl. And you've thought, that's ridiculous. A book is a good book, a character is an interesting character, regardless of gender. Besides, reading represents the ability to empathize with other human beings, and it's going to be a long, tough life for boys if they can't empathize with 50% of the population of the world!
You want the boys in your life to read books with leading girls, but at the same time you're hesitant to recommend anything to them that's too "girlie" for fear of turning them off the book and helping to cement that no-girls-allowed prejudice. Have no fear! Here are some excellent books in many genres that have female main characters but don't emphasize romance or "girl issues" (ew, cooties!).
Ps. some of them are by me. SHAMELESS.
Middle Grade
When You Reach Me by Rebecca Stead
Keeping Score by Linda Sue Park
Icefall by Matthew Kirby
Princess Academy by Shannon Hale
Rapunzel's Revenge by Shannon & Dean Hale, illustrated by Nathan Hale
Kiki Strike (and series) by Kirsten Miller
Leviathan (and series) by Scott Westerfeld
Dealing with Dragons by Patricia Wrede
Star Girl by Jerry Spinelli
Walk Two Moons by Sharon Creech
A Wrinkle in Time (and series) by Madeleine L'Engle (good graphic novel too)
Protector of the Small quartet by Tamora Pierce
The Circle of Magic (and series) by Tamora Pierce
The Cabinet of Earths by Anne Nesbit
Fablehaven series by Brandon Mull
Kat Incorrigible by Stephanie Burgis
Project Mulberry by Linda Sue Park
Where the Mountain Meets the Moon by Grace Lin
The Wee Free Men (and series) by Terry Pratchett
Palace Beautiful by Sarah DeFord Williams
The True Meaning of Smekday by Adam Rex
Mockingbird by Kathryn Erskine
The Sisters Grimm series by Michael Buckley
The True Confessions of Charlotte Doyle by Avi
Dragonflight (and series) by Anne McCaffrey
Inkheart by Cornelia Funke
Little House on the Prairie by Laura Ingalls Wilder
Howl's Moving Castle by Diana Wynne Jones
Hero and the Crown by Robin McKinley
The Blue Sword by Robin McKinley
Zita the Space Girl by Ben Hatke
Teen
Uglies (and series) by Scott Westerfeld
Liar by Justine Larbalestier
Claudette Colvin: Twice Toward Justice by Phillip Hoose
The Goose Girl (and series) by Shannon Hale
Prophecy by Ellen Oh
Legend by Marie Lu
The Adoration of Jenna Fox by Mary Pearson
Graceling by Kristin Cashore
Sabriel by Garth Nix
Blackbringer by Laini Taylor
The Last Dragonslayer by Jasper Fforde
Unraveling by Elizabeth Norris
The Books of Pellinor by Alison Croggon
The Nation by Terry Pratchett
Cold Fury by T.M. Goeglein
Heist Society series by Ally Carter
Gallagher Girls series by Ally Carter
Across the Universe by Beth Revis
The Hunger Games by Suzanne Collins
Wow, that's an awesome list of books, and I know there are many more. Let me know what I should add to the list.