Same hear Duc. They quoted me 2-3 weeks, it arrived in 11 days. Weight should have nothing to do with it.
One thing to remember is that they don't necessarily ship from Australia. They source from wherever they can. My book came from Germany via S. America.
Cool book by the way. My wife's into both!
Which in fact might be the problem. You could've stumbled onto an accidental bestseller like "Boring Postcards" (just what it says) or "Ants"(massive, expensive reference book on Ants). Neither were expected to do particularly well, both turned out to be huge bestsellers.
This looks like that sort of thing. Seemingly a limited audience, but in reality, a huge demand.
The publisher may have to print more. BTW; "Brief History's" initial worldwide run was only 10,000 copies.
On the other hand: if you chose super-saver shipping, it will get bumped behind the express orders.
PJH