Starting to plan

So i'm starting to plan my all grain system and i have a few quick basic questions that seem like common sense but anyway...

I plan on doing one tier, three 15 gallon kegs, with pumps,
hot liquor tank-> mash tun-> boiling kettle

why or do i need the hot liquor tank?
why cant i boil my water for the wort right in the mash tun?
any suggested reading material so i don't ask to many more questions?

thanks guys (gals?)

1) You don't need 3 vessels. I use my BK for my HLT currently. It can save save time and hassle however to have a dedicate pot.
2) You could do this, but then you won't have water for sparging. You don't dough in with your full volume.
3) This forum and this section is all the reading material one needs.

Have your brewed extract before or just jumping in all at once. Nothing wrong with that at all. Just gauging experience for what you may or may not currently know.

I've done three extract and am ready to move ahead, will keep do extract regularly until my set up is done, it will be some time (bills, time ect.) so yeah thanks that does help.