A brief one will probably be best.

In reference to the diffidence the author has had in presenting this work to the public, the want of talent, and the fear that the events of his life might not be of sufficient interest to warrant a publication, were the principal reasons for his unwillingness. The rough sketch which he drew up, however, was shown to a gentleman whose standing in the literary world gives weight to his opinion, and whose name is withheld only lest his credit should suffer by encouraging so poor a performance ; he recommended to the author to proceed.

Here it is, then, with all its defects. He has only to ask the continued indulgence of that public who have so long taken an interest in his case : if they will bear with him in this performance, probably he shall never again trespass upon their patience and kindness in the same way.