Yahoo CEO Marissa Mayer scored a big win this week when comScore reported that Yahoo had beaten out rival Google — her former employer — to become the top US Web property based on unique visitors during July.

That news is symbolic of the revolution that Mayer is overseeing at Yahoo, turning it from sleepy giant into vibrant Internet leader, and there’s quite a story behind it.

This impressively detailed, longform article from Business Insider’s Nicholas Carlson provides the back, front and side story to Mayer’s arrival at Yahoo — covering her early life and education, time at Google, the intriguing tale of how she trumped interim CEO (and boardroom-backed) Ross Levinsohn to her job, and, of course, her impact to date.

It’s over 20,000 words long, but well worth a read if you can set aside some time this weekend.

➤ The Truth About Marissa Mayer: An Unauthorized Biography

Update: A counter-argument to the Yahoo resurgence claim:  [GigaOm]

Headline image via Mario Tama/AFP/Getty Images