I bought a Yonex bookbag today, looks great, but I don't know how the velcro thing meant to secure the bookbag is supposed to work? Any info about this would be appreciated - thanks in advance ;D.

I don't know which bag you are talking about; please post pictures.

What did you mean by bookbag ?
If you mean BackPack, you can read this thread (http://www.badmintonforum.com/vb/showthread.php?t=21645)

I bought a Yonex bookbag today, looks great, but I don't know how the velcro thing meant to secure the bookbag is supposed to work? Any info about this would be appreciated - thanks in advance ;D.
To my knowledge, the racquet sits upside down in the bag. The head of the racquet points down and goes into the outermost compartment. Then the racquet shaft is secured using the velcro.

The racquet are inside their thermo bags, otherwise the velcro does really secure the shaft.