I appreciate the contrary viewpoint, however, for every study showing that
L-carnitine is not effective, there are others that show it is.  Many such
studies showing its effectiveness are referenced in Crayhon's book.  Also,
Robert Crayhon is not "pushing" any particular brand of L-carnitine.  Also,
he emphatically repeats in his book and when I've heard him on the radio that
L-carnitine is no "magic pill".  Rather, it has a synergistic effect to
enhance energy and fat burning when used in conjunction with a low
carbohydrate diet -- he specifically advocates a paleo type diet for health.
While nothing works for everyone (including the paleo diet judging from some
postings by people unhappy with their cholesterol readings and lack of fat
loss), there are some people who find L-carnitine works for them.  I
personally found the book quite interesting  I also feel a noticeable
difference in my energy levels when I take L-Carnitine about 30 minutes prior
to a workout.