Shares of Glu Mobile (NASDAQ:GLUU) are kicking off the new trading week by hitting their highest level in more than a decade on Monday. One of the market's hottest stocks over the past two years -- the mobile game publisher has nearly quadrupled since the start of last year -- has finally taken out the previous highs set in the summer of 2014 when Kim Kardashian: Hollywood was racing up the app charts. You have to go back to late 2007 to find the last time that Glu Mobile stock was trading higher. 

Unlike its two previous peaks, the highs this time seem sustainable. Glu is rolling on the basis of a more diversified product line than it was when a single title's hype helped send the shares surging four years ago. We're also far removed from the initial upticks behind Glu's springtime IPO at $11.50 in 2007, when it was being valued more on potential than on substance. Glu Mobile is cranking out record bookings and healthy growth, and it's hard to get in the way when the fundamentals back the big gains. 

App cover art for Kim Kardashian: Hollywood game.

Image source: Glu Mobile.

Game on 

Glu Mobile's latest financial report was another beauty. Bookings rose 20% to hit $99.2 million in the second quarter, well ahead of the $90 million to $92 million that it was targeting at the time of its first-quarter earnings call. The biggest contributor continues to be Design Home, the interior-decorating simulator that has been Glu's top draw for more than a year. 

We're not where we were in 2014 when the stock soared as Kim Kardashian: Hollywood raced up the charts, only to buckle when it inevitably started to fade. Design Home is undeniably the reason why Glu Mobile is hitting new highs right now, but the game is contributing a modest 38% of the bookings. The casual game developer sees interest for its Major League Baseball–licensed Tap Sports Baseball gain in popularity with every passing spring. Even some of its older releases, including Covet Fashion and, yes, Kim Kardashian: Hollywood, sometimes surprise with sequential upticks in bookings to move the needle here. 

Glu Mobile seems to be pushing its full-year guidance higher with every passing booking. Worrywarts will argue that its outlook for the current quarter is soft -- as $94 million to $96 million in projected bookings would represent decent year-over-year growth but a sequential dip from this year's monster second quarter -- but there's some seasonality to Tap Sports Baseball, and we've already established that Glu has coasted through its conservative guidance in the past.

The shares are still far removed from its double-digit IPO price more than 11 years ago, but it's actually earning its gains this time around. Glu Mobile has its fingers on the pulse of what casual and social gamers want and is engaging players in the process. It's the right formula to succeed, making Glu a sleeper growth stock that not a lot of people are following despite its hearty rally over the past two years.

Rick Munarriz has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.