The Adventures of Robin Hound — K. Kibbee

In book two of the series, Theodore and Sam have been transported, while reading their book together, to the land and time of Robin Hood. Now, they must figure out what happened and how to get back to the bookstore! Oh, and Theo can now speak!

Together, they will meet Robin Hood himself and, a braggadatious, slow-moving dog suspiciously named Robin Hound. After Robin Hood and his merry men take Sam and Theo's magical book, the two must rely on Robin Hound to get them to Hood's camp and take back the book - their only way home. 

Along the way, they will discover that Hound is not all he makes out to be and Theo will have to come to the rescue on more than one occasion. Stealing the book back from Hood and his Merry Men, will not be an easy task.