The term 'book END' can be broken down into seven crossword solutions: INDEX (5 letters), FINIS (5 letters), LET (3 letters), ISH (3 letters), APPENDIX (8 letters), KAY (3 letters), and ING (3 letters). INDEX is a list of contents or topics found at the beginning of a book, while FINIS is a Latin word meaning 'END' or 'CONCLUSION'. LET is a verb meaning 'to allow' or 'to permit', while ISH is an informal suffix used to indicate a slight degree of something. APPENDIX is a section of a book containing additional information, while KAY is a female given name. Finally, ING is a suffix used to form present participles of verbs. Together, these solutions form the term 'book END', which refers to the two ends of a book, usually decorated with ornamental designs.