The text is bilingual English/Spanish and documents Arenal's activity from 1968 to date.
The only shortcoming is that I would have preferred more text, but the photographs more than make up for this. Photographs include a rare pre-1968 photograph, as well as good coverage of the aftermath of the 1968 Vulcanian eruption, and various activity over the past 40 years. There are lots of good night-time photographs of incandescent lava and Strombolian activity. Also included are some excellent time-lapse stills of pyroclastic flows. These are amongst the best photographs that I've seen for portraying the speed and unpredictability of pyroclastic activity.