I'm going to purposely leave Terry Pratchett books off this list, because otherwise they would dominate it. But let it be known that I heartily recommend them to everyone, especially Night Watch, The Truth, and Soul Music.
I've also decided to divide this list up by themes, and spread it across several posts. The first theme will be books that deal with feminism or strong female characters, explicitly or vaguely.
Without further ado, may I introduce:
Natalie's Official and Fully Endorsed List of Exquisite Books for Reading (Part 1: Vaguely Feminist)

One incredibly good series and one equally incredibly good start to a series. The Gemma Doyle Trilogy is a wonderful set of dark fantasy novels set in Victorian England, and the Diviners is the first in a new trilogy of dark fantasy books, this time set in 1920s America. Really absorbing reading, and they contain some of my favorite female book characters of all time.

When Everything Changed, by Gail Collins
Nonfiction this time, but very well written. A history of American feminism and the evolution of gender roles, starting in the 50s if I remember correctly. Surprisingly easy to read and absolutely rife with interesting information. One of the better birthday presents I've received. Thanks Laura!
The Warrior Queens, by Lady Antonia Frasier

and some others I can't remember off the top of my head. Scholarly but absorbing, and I found it especially interesting that the author kept bringing up archetypes for warrior queens throughout history, like the Holy Armed Figurehead and the Appendage. Incredible book, overall.
Pope Joan, by Donna Woolfolk Cross
Just finished re-reading this incredible historical fiction novel. The existence Pope Joan, also known as Pope John VIII, has been greatly contested by the Catholic Church since the 17th century. This book lends marvelous character and depth to the story of the only female pope. Interesting from a feminist perspective and a historical one, because it paints a dramatic picture of the 9th century in Europe. I highly recommend it.
Tune in next time for the continuation of my list!