The tenth book of the Aṅguttara Nikāya, the Collection of the Numbered Discourses of the Buddha, collects 746 suttas or discourses whose subject matter is centered on groups of ten topics. The most frequent are the eight components of the eightfold path expanded to ten and also ten components of ethics. 
This book is especially thick because of the continuous repetitions upon repetitions with very slight variations. The volume is also notable for including extensive content on monastic discipline. 
As the most outstanding sutta we have AN 10.26: With Kāḷī. Fierce criticism of the Brahmanical meditation methods called "kasinas" which, in early medieval times, were included by Buddhaghosa in his entrance work to a famous Sinhalese monastery and which today some claim as "effective" methods of meditation within Buddhism. 
The most interesting suttas in this volume are: 
AN 10.6: Contemplation. Perceiving without perceiving. One of the most curious things one feels when entering current. 
AN 10.14: Emotional Sterility. Doubts about the Master cause emotional sterility. 
AN 10.19: Abodes of the Noble Ones (I). When one stops searching. 
AN 10.29: Kosala (I). Tremendous criticism of wrong practice. 
AN 10.31: With Upāli. The reasons for the establishment of the monastic code. 
AN 10.64: Faith. On those who have entered the stream. 
AN 10.65: Happiness (I). Family and friends who get together and annoy you. 
AN 10.76: Three things. A beautiful sutta on renunciations. 
AN 10.92: Dangers. Teaching on perishability and faith. 
AN 10.108: Physicians: Interesting sutta on physicians and the list of diseases known and treated with varying degrees of success. 
This book does not contain false suttas. 
In summary, this time the arduous and exhaustive work of research and reconstruction in comparative linguistics has been especially dense and thick.