This section is from the book "Real Property, An Introductory Explanation Of The Law Relating To Land", by Alfred F Topham. Also available from Amazon: The New Law Of Property.
A contract for the sale of land may be a very simple matter; it must be in writing, but otherwise there is no special formality required. So also, the conveyance requires simply a deed executed by the seller. But in practice a sale of land may become a most complicated matter, requiring the greatest care and a sound knowledge of all the rules of real property law. A chattel, such as a piece of furniture, is usually sold without any investigation into the right of the seller to deal with it as his own. For the person in possession of a chattel is prima facie the absolute owner of it; if he has parted with his ownership, or mortgaged it, these transactions can be discovered by inspecting the register of bills of sale, and even if he is a thief, the buyer is protected if the sale is in market overt; and if the sale is bad, he has his remedy against the seller for damages and can usually obtain a similar chattel elsewhere.
Land, however, as we have seen, may be in the possession of a person who has merely a yearly tenancy, or a life estate, or he may have mortgaged it or bound the land by restrictive covenants, and if the buyer, after completing his purchase, is turned out of the land, or prevented from using it in the way he wishes, no other piece of land can be exactly the same, and he may have spent large sums on building and improvements.
Thus, a purchaser of land must make careful investigation and demand strict proof from the seller that the land is really his.