The National Geographic Map series is a decent one, but this has a few glaring inaccuracies that make it untrustworthy for travel in Costa Rica. For starters, the roads and their markings are incorrect in a number of places; many roads were paved when they were marked as dirt (such as the trip from Union to Nuevo Arenal). Some landmarks were not on the map at all (Los Patos in Corcovado is not there, Sirena is on there twice). The division of the country right in the middle also makes it hard to navigate between the two sides.
It is very readable and clear, but between a lack of highlights on the locations, inaccuracies, and the size of the thing it makes the map not particularly useful for travel - there are far better options. I'd recommend the Toucan map series instead.