After failed summer flings with Bradley Cooper and Gerard Butler, Jennifer Aniston and John Mayer are back on, reports the new issue of Us Weekly (on stands now).

"He really got to her, and she's hooked on him," a source tells Us. "She just can't let go."

The couple first got cozy in April 2008 after spending five sexy days together in Miami, but went on to split twice -- most recently in January 2009.

A source close to Mayer, 31, tells the new issue of Us, "They are very close. They remain great friends. He thinks she's amazing, nice and smart, and he has nothing but respect for her."

Although they dined separately in NYC on Sept. 22, a source tells Us they met later that night at the Four Seasons Hotel. Other reports have claimed they've been texting each other and recently dined with Aniston intimates Courteney Cox and David Arquette.

See what Jen -- and other stars -- look like in a bikini

Aniston, 41, has said she "deeply, deeply cares" about Mayer, whose next album, Battle Studies, hits stores Nov. 17.

Seconds a source to Us: "There's something about John that she just can't resist."

For all the juicy details of Aniston and Mayer's secret meetups, why their friends don't approve of their reconciliation and why they may not last this time around, pick up the new issue of Us Weekly.