Now let me just say right off the bat that I'm not a bibliophile by any means.
The covers are cloth with dark blue writing and the image is pasted onto the front of the book.
Each one has a few cute illustrations.
This one is dated 1915.
The Bobbsey Twins was one of the longest running series with 72 books beginning in 1904, the last book being published in 1972. Here is the excerpt about these books:
This one is dated 1907 but sadly the back is in very poor condition :o(
I love to think about children reading these books back in the day... before video games... before television... when reading and playing outdoors was what children did :o)