I just found this book in pdf format. I think there has been some intresst on the forum for it.

THE TREATISEONTHE METHOD OF VIPASSANA INSIGHT MEDITATIONWhich can speedily lead to the attainment of Magga-Phala-Nibbāna

http://www.saraniya.com/books/mahasi-sayadaw/pdf/mahasi_sayadaw-vipassana_treatise_volume_i_part_i.pdf
http://www.saraniya.com/books/mahasi-sayadaw/pdf/mahasi_sayadaw-vipassana_treatise_volume_i_part_ii.pdf
http://www.saraniya.com/books/mahasi-sayadaw/pdf/mahasi_sayadaw-vipassana_treatise_volume_ii_part_i.pdf
http://www.saraniya.com/books/mahasi-sayadaw/pdf/mahasi_sayadaw-vipassana_treatise_volume_ii_part_ii.pdf

Enjoy
Gunnar