As a fan of the light novel Re:Zero I found this books as a way of understanding the side characters better. If you want more of Re:Zero and its history in the past 100 years is a great way of discovering it. The characters are well written and the stories still gives us awesome fight scenes and drama we get in the main series. Though, some parts where boring and even though they were added for character developing I had to force myself to finish it, especially The dream of Lion King. The main main happenings were well explained to me, since a lot of manga/lnI have read where going with a main happening which wasn't clearly explained.
Frist we have The dream of Lion King which shows us the story of Crusch and the second one, The Love Song of the sword divel which is about Wilhelm and Theresia.