Since I haven't read the 'lost without love novel', it's difficult to say exactly who the main characters are. However, based on the title, they are probably individuals who find themselves in a difficult situation due to the lack of love in their lives. They might be lonely hearts, or people who have lost love and are now trying to find their way back. It could also include characters who have never experienced true love and are searching for it.
Not having read the 'lost without love novel', we can only make assumptions about the main characters. They could be characters from different walks of life, all united by the common thread of being 'lost without love'. There might be a young adult who has just come out of a bad relationship and is feeling lost and alone. Or perhaps an older person who has lost a long - term partner and is struggling to adapt to a life without that love. There could also be a character who has always been single and is starting to realize that the lack of love in their life is causing them to feel unfulfilled and adrift.