Your start-up days are long behind you.

And boy, that’s a relief. It was a struggle, for sure, but you made it – and now you’ve got your eye on making the Fortune 500. To do that, your business has to stay alive and maintain its mid-level status, and in the new book “Mighty Midsized Companies” by Robert Sher, you’ll find out how.

In the past few years, a lot of press has been given to small businesses. Even politicians focus on them, but Sher says that midsized firms – those with revenue between $10 million and $1 billion – make up a third of the GDP.

That those midsized firms are rarely studied may come as a surprise since, without the flexibility of start-ups and lacking the financial strength of mega-corporations, midsized businesses have their own unique problems and hurdles.

To overcome the issues and thrive, Sher says there are “Seven Silent Growth Killers,” of which all CEOs of midsized firms should know and be mindful.

A lack of discipline, not heeding deadlines, and believing that there are enough hours for anything is deadly for a midsized business. Wasting time – or letting it slip away – is the Number One growth killer.

Messing with your core business is killer Number Two. If you’re tempted to tinker, hire someone to keep you on-track (Sher recommends a good CFO).

Learn the value of strategic planning and don’t waver from that plan by purchasing other businesses, willy-nilly. Yes, he says, acquisitions can help a midsized business grow, but strategy is the key to doing it right.

Keep an eye on assets (including staffing numbers) as you grow, to ensure you’re able to handle the extra work and can avoid an “operational meltdown.” Watch your cash flow carefully, to shield yourself a little better from problems beyond your control. Become good friends with your bank, but think twice before asking investors for money. And finally, hire with an eye toward leadership. Good leaders in all levels of your firm will give you a leg-up on the competition.

Without a doubt, “Mighty Midsized Companies” is a pleasant eye-opener.

It’s readable, for starters, so that even the newest of newbies can tackle it with optimism – but yet, it’s thorough enough that any midlevel C-Suiter could garner a wealth of information from it, too.

That info comes with a sense of urgent patience inside no-nonsense advice.

Sher uses true and sometimes cautionary tales to make clear why it’s imperative for middle-of-the-pack firms to keep watch for those insidious things that could start the end of a business, and he does it without talking up or down to his readers. I appreciated that face-to-face feel; it seemed more approachable – therefore, more useful.

For sure, this is the book to read if you fall into Sher’s definition of a midsized company, but I also think smaller businesses would benefit from what’s inside.

If you want to keep your business going – and profitable – “Mighty Midsized Companies” is a book to start up.

Terri Schlichenmeyer’s reviews of business books are read in more than 260 publications in the U.S. and Canada.