The cover of the book 'Professional Android' by Reto Meier, fourth edition. The cover features a robotic arm with a butterfly-like structure on its end, set against a dark background with a gradient from dark to light. The title 'Professional Android' is prominently displayed in large, bold font at the top, with the subtitle 'Building Android Applications' below it. The author's name, 'Reto Meier', is centered at the bottom of the cover. The cover also includes a logo in the top left corner and a tagline 'Join the discussion at p2p.wrox.com' in the bottom left corner.