What are some of the best relationships you've read about?

Brother/sister: My Heartbeat by Garrett-Freymman Weyr and The Perks of Being a Wallflower by Stephen Chbosky

Male friends: Sins of the Fathers by Chris Lynch

Mother/son: Someday This Pain Will Be Useful To You by Peter Cameron

Female friends: The Sisterhood of the Travelling Pants

I have this book on my TBR list. Definitely moving it up in the pile after reading Nathan's post. As for your question...I'll have to think a little bit more about it. But off the top of my head, the relationships in Circle of Friends were pretty complex and interesting to me. I definitely love the up-and-down moments of relationships in fiction. I like feeling both happy and sad while reading about them.

Brother/Brother: Break by Shady. No joke. The relationship Jonah and Jesse have together is amazing.

Girlfriend/Boyfriend: The Darkest Powers Trilogy between Chloe and Derek. If you want to read about a REAL paranormal relationship this is it.

Bilbo Baggins and Gandalf: Enough said. Dude.

General: The Outsiders. The relationship all the boys share is really unique.

I agree about The Outsiders, too.

The relationships between the girls who are frenemies in Some Girls Are by Courtney Summers were pretty complicated and awesome, in my opinion.

I second Nathan on the LFA recommendation.

almost-romance chemistry b/t friends: The Disreputable History of Frankie Landau-Banks
an almost-symbiotic relationship: Willow
a couple that just clicks together: Nick and Norah's Infinite Playlist

This is a really good thread. It's got me thinking about the dynamics of my own characters...

Seconding Some Girls Are and thirding The Outsiders

All of Sonya Hartnetts novels have that edge where the dynamic between the characters just fill you with a dread/suspense because you know something is going to go down...It's hard to isolate which ones best illustrate this, but here's a few:
Sleeping Dogs: brother/sister relationship that becomes incestuous.
The Devil Latch: Kitten (18yr old male) and Aimee (18yr old next door neighbour). Kitten psycholgically seduces her (and the reader) with creepy results. Very intense.
All my dangerous friends: Mate, all the relationships in this. Wow. You forget to breathe while reading this one.
Princes: Beauitiful Twin brothers, Indigo and Ravel, who live isolated in a rat-infested mansion. Their relationship is dark and sinister.
In Surrender, a childhood blood brother pact between friends Gabriel and Finnegan, ends in arson attacks, psychological games and murder.

For dynamics in romance:

Jonah and Taylor in On The Jellicoe Road - Melina Marchetta.

And, for general sexiness, steamy-ness, simmering damn hot chemistry :
John (Officer After) and Meg in Going Too far - Jennifer Echols

When I was a little kid, I liked the relationship of Frodo and Sam from Lord of the Rings. Over the course of the story Frodo went over the edge and back, but no matter how horrible Frodo got, Sam stuck by him and did what he could.

It's an odd combination of friendship and brotherhood. Apparently Tolkien based Sam off the army batmen that served commissioned officers during WWI.

As a side note, that's why one of the most piss-off things about the movies was when Sam abandons Frodo. That never happened in the book, and to me, it tarnished what Sam is supposed to be -- the hero that will never, ever, abandon his friends and duty.

Seconding Jonah and Taylor from Jellicoe Road

And adding a new one. Best friends: Leisel Meminger and Rudy Steiner from The Book Thief. I'm not even sure what tag can be attached to Leisel's relationship with Max in that book, but I'd say it's pretty freaking dynamic and awesomely written.

Also adding the strange relationship between Margo and Q in Paper Towns by John Green. It's a romance, but not a typical one.

I second My Heartbeat for brother/sister, male/male, and girl/guy relationship. It's just an amazing book.

The stepmother/stepdaughter/stepsister relationships in Bound by Donna Jo Napoli -- it's a Cinderella story on the surface, but her characters are so complex, and their relationships to one another are even more so. The stepmother is not totally evil, in fact you can almost sympathize with her, even though you hate her for it sometimes.

And not to spoil for those who haven't read, but the sibling relationship in Cassandra Clare's City of Bones (and the rest of the trilogy) was really interesting... Once you recover. From. Well. >.>

The relationship between Jenna and Cameron in Sweethearts by Sara Zarr was just flipping fantastic. Completely believable and deep, deep, deep.

I love the friendships between Em, Cass and Lyd in Jaclyn Moriarty's Finding Cassie Crazy (The Year of Secret assignments). In so few words, Jaclyn captures their intimacy and awesomeness and everything that's cool about best friends in high school.

They get a few cameo appearances in 'The betrayal of bindy macKenzie' and some major roles in 'Dreaming of Amelia' (The Ghosts of Ashbury High). * I especially like how other characters comment on the girls and their relationship. Funny, touching stuff. I hope Moriarty re-vists them, but now they're finished high school, it seems unlikely

Oh, and Danny Clarke and Nile in Adrian Stirlings Broken Glass.
Perfectly captures that uneasy friendship of trying to impress another and turning bad bad bad...

* why do all Moriarty's books have multiple titles? It's annoying...

Eilir and Astrid from "Dies the Fire" emberverse trilogy by S.M. Stirling

Also Rudi and Matilda from that same series.