For the County and City of Derry~Londonderry, printed Lists of Absent Voters survive, along with three manuscript volumes entitled 'Record of Absent Voters'. There is a printed list for each of the three Derry~Londonderry constituencies (Londonderry City, North and South Londonderry), further divided by Polling District and Registration Unit.
Londonderry City is divided into Polling Districts which equate to the City wards. Within each Registration Unit or Ward the voters are listed by Street (in towns) or townland. There is also a manuscript volume for each of the three Derry~Londonderry constituencies. Absent voters are, for the most part, arranged alphabetically by surname, further grouped by Registration Unit or Ward within each letter listing (PRONI Reference LOND/5/1/7).
PRONI has created an index giving the Surname and Forename of each absent voter, along with information on the Polling District, Registration Unit and address that is: Street or Townland. It also gives the Constituency and page numbers for both the printed and manuscript lists, which you can use to identify individuals in the digitised version of the Absent Voters Lists. The digitised Lists includes details of the voter's military unit rank and service number, if they were Naval or Military voters.
It would appear that the manuscript alphabetised volumes were created after the printed lists, most likely to aid access when making updates in preparation for the 1919 register. Due to the inclusion of updates, information about individuals may vary within the printed and manuscript lists, so it's recommended that you look at both when carrying out research.