40" is a standard size for a wrist watch. Anything smaller would look like a unisex or female watch. I have really thin wrists but 40" even then is still a good size. As it has a really slim profile (8mm) it should be perfect.
As for the watch itself, it is a solid quartz movement by the looks of things, but it has basically no water resistance. Literally washing your hands and not much else. Also, remember that if you're buying off teh internetz you will need to get it adjusted for your wrist size after purchasing it. You may want to buy an adjuster of Amazon itself (like a gun thing, which pushes a needle in to the bracket so you can adjust it yourself - REALLY easy to use), and they're only £5ish - most jewellers charge £10 to adjust wrist watches.