Fairy Tail Volume 16 by Hiro Mashima
The Laxus story arc (where Laxus tries to take over the Fairy Tail guild by having everyone fight each other, leaving him in charge) ends with the unsurprising defeat of Laxus. The very ending of the arc is sweeter than expected. Then the guild has their fantasia celebration as part of Magnolia's harvest festival (Magnolia is the town where the Fairy Tail guild hall is located). A new storyline starts with several Dark Guilds teaming up to seize control of a special ancient magic called Nirvana. Fairy Tail teams up with other guilds to send their top wizards to fight the Oracion Seis, a Dark Guild with only six wizards. Naturally they are supremely powerful wizards so the fight will not be easy.
The book also has a side story about Lucy's father, who has fallen on hard times. It's also sweeter than expected but does seem more like filler than part of a greater story arc.