Young-adult authors are like rock stars to their young fans. Put four such writers together at one location, and it's a mega-concert. Blue Willow Bookshop hosts the SWEAT (SoCal Writers' Excellent Adventure in Texas!) tour with Debra Driza, Shannon Messenger, Amy Tintera and Kasie West. The group of novelists has taken their show on the road to connect with their clamoring fans (and to sell and sign a few books along the way). ''We are seeing more of this collaboration between authors,'' says Valerie Koehler, self-described ''Girl Boss'' at Blue Willow Bookshop, the local stop on the tour. ''They love the interaction and the new audiences. Harry Potter got everyone reading children's novels,'' Koehler tells us. ''Twilight got the teen girls excited, and The Hunger Games hit it out of the park. There is a huge fan base…around the world.'' Hosting multi-author signing events is fun, Koehler adds. ''The authors always play off each other; it's usually fast and fun with lots of laughing. There are lots of questions from their fans, and always lots of pictures!'' Yep, just like a mega-concert.