Pharmaceutical companies actually call the side effects "adverse reactions" on their "scare sheets". Contraindications are known preexisting conditions that might rule out the use of a particular drug. The list of adverse reactions and potential drug interactions is lengthy because every reaction during the testing trials is listed, whether known to be caused by the drug or not. Many of the reactions would have occurred regardless of the drug. This is a small but important point, and it shows the lack of any critical review taken in publishing this book. Each statement of a scientific basis for the claims calls for more skepticism.
The structure of cyclocreatine is fairly flat (planar), which aids in passive diffusion across membranes. It has been used with success in an animal study, where mice suffered from a SLC6A8 (creatine transporter at the blood brain barrier) deficiency, which is not responsive to standard creatine supplementation.  This study failed to report increases in creatine stores in the brain, but noted a reduction of mental retardation associated with increased cyclocreatine and phosphorylated cyclocreatine storages.  As demonstrated by this animal study and previous ones, cyclocreatine is bioactive after oral ingestion   and may merely be a creatine mimetic, able to phosphorylate ADP via the creatine kinase system. 
As an Austrian brand, Head has always placed a premium on race results, and their investments in this area are paying impressive dividends. Lindsay Vonn has already eclipsed the considerable achievements of Bode Miller; both are Head skiers, as is Ted Ligety, who may be the second best technical skier in the world today. In a sport where wins can be measured in the thousandth of a second, who comes out on top may appear serendipitous; when athlete after athlete is holding up a crystal globe recognizing a season of superiority, something other than serendipity is afoot.