-Adds new book. 'book' is location of HTML help project (hhp) or ZIP file
-that contains arbitrary number of .hhp projects (this zip file can have
-either .zip or .htb extension, htb stands for "html book").
+Adds new book. {\it book} is URL (not filename!) of HTML help project (hhp)
+or ZIP file that contains arbitrary number of .hhp projects (this zip
+file can have either .zip or .htb extension, htb stands for "html book").