To be perfectly honest, I haven't read two of the four books listed here, but Goodreads doesn't want to let me break out the Gentle Animals one, so I'll just review that here and you can read my review for Bendon Bear and the Wild Animals if you're curious about that.
The Gentle Animals one was actually less interesting because it went for cute and fluffy rather than informative and engaging. I still like the way the drawings of Bendon Bear interact with the photographs of the various animals, but this one felt a little silly. Also, I have no idea why a dolphin and a cat are in the same book, especially since dolphins aren't what I would categorize as "gentle."
The two of the series together rather the 3 stars, but I would give the Gentle Animals 2 stars only.
Update 1/22/16: I've now read "Bendon Bear and the Forest Animals." It, I think, is 2.5 stars--I may be biased because it includes the wolf, which is one of my top five favorite animals. This collection made more sense in terms of which animals were included, but unfortunately the text was a little less cohesive--the short paragraphs were a lot more about what Bendon was doing rather than what the animal could do (the balance of the two was off). It was cute for Bendon to meet another bear and be friends, though...even if it did smack of thieving the Pooh Bear imagery and conceptualization. Still very cute, and this is a good series to introduce kids to animals.