That first one is basically the previous edition (2000) of Peter Hiscock's newer book (2003) in Erin's second link. Neither are as good or comprehensive as his (Mini)Encyclopedia books.
The book in your second link I have as well, so I can compare them!

It's almost like a well presented high-school book with pages of long paragraphs of written information with small pics and basic diagrams. Almost like one of those 'Idiot Guide to..' books, but nicer to look at. Just as informative text as the Mini-Encyclopedia, probably more (because there's lots more words), but nowhere near as nice or easy to read and understand, and nowhere near as good a plant identification section as the Mini-Encyclopedia.
To put it simply, if we were talking about a guide book on how to start your own vegetable garden with everything you need to know in a nice and easy to read and understand format with lots of great pics, showing step by step photos on soil, how to plant, trim roots, fertilizing, spacing, garden layouts, etc, and then with a big section of pics of all the different varieties of vegetables and their specific needs etc, the Mini-Encyclopedia wins that category hands down.
I see the Mini-E is available on Amazon second-hand for $10 or less. Much better value used than the Simple Guide new at $11 I think!