Stars rise, stars fall: it’s an inescapable part of business life. While Steve Ballmer is in descent, Marissa Mayer, CEO of Yahoo!, seems very much in the ascendant. If you want to get a sense of why, you’d be well advised to set aside an hour to read Nicholas Carlson’s excellent Unauthorised Biography of Marissa Mayer.

The Business Insider article takes in the salient parts of Mayer’s childhood, time at Google and her first year as the person in change of Yahoo! – and it makes for compelling reading. In some ways, she makes a fascinating counterpoint to Ballmer. He was a business-focused guy in a time when the company needed a product visionary. Carlson makes it clear that Mayer is very much a product-focussed person – and that may be exactly what the company needs. There’s an interesting quote from Marc Andreessen:

Andreessen talked about the difference between technology companies and “normal” companies. He said the output of normal companies is their product: cars, shoes, life insurance. In his view, the output of technologies companies is innovation. Whatever they are selling today, they will be selling something different in five years. If they stop innovating, they die.

That certainly seems to make Mayer an ideal fit for the role. However, it’s interesting to note that Carlson’s preferred explanation for the stalling of Mayer’s career at Google – or at least the appearance of it, as she slid down the reporting ranks – is that she wasn’t interested enough in the business side of the company. Survival of any company requires a close alignment of the product and commercial visions – anything else is, at best, charity or, at worst, a hobby…

We know that Mayer can do product. What she needs to prove is that she has learnt from her sidelining at Google, and can now combine that with business – and services – to create a viable company. Carlson’s article is a compelling read because it presents a nuanced picture of a woman who could be capable of that – but who could also be capable of micro-managing her way into an utter disaster…