Antiquarian
The best source of antique books is the local library. After knowing the names and types of books required, going to a bookstore that specifically stocks antique books, or online shops such as eBay might be the best bet.
Antique books can be purchased on eBay, Amazon. The Bookfinder website also has many titles one can choose from. One can search by title, author, even by country to locate antique books to purchase.
Some good books for learning about antique tractors include Antique Tractor Bible: The Complete Guide to Buying Used Tractors. You can read more http://www.amazon.com/Antique-Tractor-Bible-Restoring-Motorbooks/dp/0760303355
A local antique dealer can appraise or someone with the Library commission can research the estimated value of an antique book. It is important to ask someone who is trustworthy in the antique dealing field.
county assessor
Classic Rare Books would certainly have rare and antique books for sale in London, although one must have an appointment in order to do so. This store is the pinnacle store of that nature though there are several others to be found throughout the city.
A person can find a plethora of places to buy antique books but one example is Patrick McGahern Books. This company offers online sales as well as purchases within their stores. One location is located at 301-368 Dalhousie Street Ottawa, Ontario Canada.
Bath has many beautiful antique shops. On the upper side of bath, you will find many antique stores for items such as furniture, ceramics, glass, textiles, books, maps, and so much more.
A variety of photographs of the exteriors of antique Ford vehicles can be found in one of the many antique car books available by visiting a local book store. Different antique car calendars will also have pictures of old Ford cars.
There are some ways that will help one identify antique books. Check the condition of the book, determine the value of the book by some experts and check the basic information of the book such as title, author, publisher, etc.
Leather books can be found at specialty bookstores, antique shops, or online retailers that specialize in rare and antique books. You may also find leather-bound books at auctions or estate sales. Be sure to verify the book's authenticity and condition before making a purchase.
I don't know of any websites that appraise magnets, you could try to take them to an antique store. The best bet would be to list them on ebay with a reserve price and see what you can get for them.