To ascertain the value of a book is an exceedingly difficult operation; in fact, there are many who assert that it is impossible to do so. Booksellers' prices, as disclosed in their catalogues, are not much to go by, for it is notorious that a West End dealer will often charge more than one who is established further East. Again, some London booksellers charge more or less than provincial ones, according to circumstance and the character of their customers. Until recently there were only two ways of becoming an adept in this department, the first and best by practical experience, a method which is not, of course, available to any but dealers and their assistants; and the second, by indexing retail catalogues and striking an average. A third method, that of taking the average of auction sales, was not available until recently, for it is too troublesome, for any save those whose business it is, to attend sales by auction all day long for nine months out of the twelve, in order to obtain the necessary materials. In 1886, I conceived the idea of fully reporting all sales of any importance taking place either in London or the provinces, and in December of that year the necessary arrangements were completed, with the modification that for the present, at any rate, no notice was to be taken of any book which did not realise at least 20s. by auction. This publication, the success of which amply demonstrates the necessity for its existence, is named _Book Prices Current_, and already five volumes are published, and a sixth will be ready at the beginning of next year (1893). As a book of this kind would be useless without a full index, the greatest possible care has been taken to make it as complete and as accurate as possible. From _Book Prices Current_ a very good idea of the average value of almost any book may be obtained. Careful note of the way in which the particular volume is bound must, of course, be taken, for this, as might be expected, makes a great difference in the price.