I've long been fascinated by Elizabeth I, and this biography, by Alison Weir, is the best I've read. The others focused solely on Elizabeth's struggles with the religious strife in England during her reign or solely on her courtships and possible marriages and, of course, the hot topic of her legendary virginity.
Weir does a good job of balancing these two vital issues, while also spending a fair bit of time on what life was like in the royal court and on Elizabeth's very real problems. For being the most powerful woman in the world in an era when women were considered property of men, Elizabeth was a bit of a mess. She wavered on decisions, she made snap judgements and then regretted them, she flirted shamelessly with men and demanded their undying loyalty, and she couldn't make up her mind on what to do with her cousin, Mary Queen of Scots.
But when you learn about Elizabeth's life, you understand a lot more why she was such a mess. She was her father's favorite child, at least until her mother, Anne Boleyn, fell from grace and was executed. After her mother's death, Elizabeth was sent pretty much into exile, only being allowed at court when her stepmothers permitted her. When her old sister Mary, a devout Catholic, took the throne, all Protestants, including Elizabeth found themselves at risk of imprisonment and/or execution. Elizabeth even spent time in the Tower of London - the prison part, not the royal apartments. Once she became queen, everyone around her wanted her married off, which would have meant that she wouldn't be the real ruler of England. Whomever she married would have become King and taken over control. Throughout her reign she lived in fear of a possible uprising by any number of factions that claimed stronger rights to the throne that she supposedly had as a woman. She feared naming an heir, believing that if she did she would probably be murdered or taken from the throne in favor of a male.
Even though she was indesicive and insecure, she held her ground through it all and brought the country through some terrible times. She was much loved by her subject, and her ragtag navy defeated the Spanish Armada. That victory alone secured her place in the hearts of her subjects.
Speaking of Elizabeth I, if you get a chance, watch the newish miniseries with Helen Mirren and Jeremy Irons. It's not always entirely accurate, but it is spellbinding. Helen Mirren does an amazing job of showing Elizabeth's many sides.