book to be in four parts or not?

My book is already in four parts and is called as Book I, book II, book III and book IV, each of about 125 pages or so, and a total of 500 pages.
Book I deals with the intended attack on Ayodhya in 1026AD by Syed Sallar Jung Ghazi Mian, grand-son of Mahmud Ghazni,and his slaying by a Bhar Raja Suheldeo to save King Veeram Deo of the Raghuvanshies.
Then the decision of the then sovereign Jaichand of shifting the last Raghuvanshy King of Ayodhya Nain Deo to the forest fortressed Katehar in Varanasi and marrying him with his grand-neice Bindumati, whose children we are all,the Raghuvanshiesof today.
After the fall of the Gaharwars dynasty,it was the turn of the Raghuvanshies of Katehar to attain the status of “Hindu Kings”,as for as the history books go,but we remained tillers of the soil, notwithstanding 400 horse’s cavalry and 5000 foot soldiers at our disposal to maintain our status as “independent land-owners” for 600 years till 1793AD.
Somehow,we attained the benediction of Ghiasuddin Tuglaq (1321AD), Sikander Lodi and finally Sher Shah Suri(1545AD),who did not seek any cess from us either.
Book II, deals with the famous Permanent Settlement of Lord Cornwallis(1789-1793) and all the intricacies of revenue law and matters, drawing from my own experience in 626.04acres of our alluvial-riverine land gone on the other side of river Gomti in 1980.
BookIII,is a lucid translation of Raghuvansh-Mahakavya by Kalidas,describing the journey of the first world-conqueror, Raghu, the great grand father of Ram.
BookIV,is about Ayodhya’s transit through 1194 to the 1st war of independence fought thro Awadh to Aarrah and the exploits of Veer Senani Kunwar Singh-Tegva Bahadur, with whom my own ancestor Jaipal singh joined and died fighting.

Will it be a good idea to publish the book in four parts to make it light weight and more convenient to carry-about? Besides a smaller price-tag and selected customer preference, like many guys may never want to know anything about Duncan’s permanent settlement, except those concerned with it in the past, hence curious.

Please advise on the issue of multi-facet production of the book. Phone me, by and by, and send guidance by email. Thanks.

Sincerely.
Suresh Pratap Singh, at Mumbai.15.05.09