I haven't found anything bad... yet ;-) This book handles all the birds in Eritrea, Djibouti, Somalia, Ethiopia and the Socotra Archipelago. One thing they could have included is a (short)list of good (or promising) birding areas + description in the respective countries, or an overview and description of different habitats. This would make the book slightly heavier, however.
Some illustrations have lines in between the drawings, to simplify which bird is which drawing. This is a usefull feature more birdbooks could have.