This game is a follow up to last year's Hyperdimension Neptunia mk2 which I'm still currently playing through. The battle system looks to be identical with some improvements to the UI. Looks like this game is going to be filled with more fanservice than the previous Neptunia games with just as much "moe" otaku filled goodness. The Japanese release date is on August 30th and will cost 7,329 yen (about US$93) and a limited edition is available at 10,479 yen (US$133).
There are currently no news regarding a US version but I assume NIS America will announce it sooner or later.