Hartmut Esslinger/Designboom

Apple fanatics may find themselves foaming at the mouth over some retro conceptual Mac computer photos featured in Hartmut Esslinger's book Design Forward: Creative Strategies for Sustainable Change.

The opus, released today in limited quantities, explores Esslinger's journey as a German designer who worked with the likes of Sony, Louis Vuitton, and others before moving on to Apple in 1982. Apple hired Esslinger (and his company Frog Design) to transform the successful yet scattered startup into a brand with a globally recognizable design mantra.

Along with many other fascinating details, Design Forward reveals how Apple originally contacted Esslinger's firm Frog Design after learning of a similar move by Xerox. At the time, Xerox employed the Richardson Smith design agency to develop a single design-language that could be used across the company.

The book sheds light on some stunning Apple product concepts, many of which came to fruition years -- or in some cases decades -- later. In the gallery belew, you can see more of Esslinger's prototype Mac desktop computers, a phone, a laptop, and even a tablet. Good luck getting a copy of Design Forward, though, as Arnoldsche Art Publishers informed CNET that a strong surge of pre-orders may push general availability back to later this month or early March.