Since I don't have first - hand knowledge of this light novel, it's difficult to say precisely. However, considering the words 'tantei' which means detective in Japanese and'mou shindeiru' which means already dead, it could be a story where a deceased detective has some unfinished business in the world of the living. It could be full of mystery, with the detective using his or her skills from beyond the grave to solve cases that were left unresolved during their lifetime. There might also be complex relationships between the detective and the living characters, and the story could be set in a fictional world with its own set of rules regarding death and detective work.
I'm not entirely sure if it's extremely popular on a global scale. However, in the realm of light novels, if it has a captivating plot about goblins being strong or having some sort of interesting power dynamic, it could be popular within the niche community of light novel enthusiasts who are into fantasy - themed stories.
The title 'Shimekiri Mae ni wa Yuri ga Hakadoru' might suggest that it could involve a yuri (female - female relationship) theme. However, without reading it, it's hard to say more. It could be about the development of such a relationship before a certain deadline or separation (shimekiri mae).
The 'goblin wa mou juubun ni tsuyoi' light novel could potentially explore the concept of goblins in a different light. It might delve into their society, culture, and how their strength plays a role in their world. For example, it could be about a goblin tribe that has evolved to be powerful and is now dealing with the consequences of that power, like interactions with other races or internal power struggles within the tribe. This could make for an engaging and unique story within the light novel genre.