diff --git a/book/book.toml b/book/book.toml
index 3250808..c7cf5c0 100644
--- a/book/book.toml
+++ b/book/book.toml
@@ -33,6 +33,7 @@ highlight-style = "./custom.theme"
 # that supports fallback fonts, which we need for emojis.
 pdf-engine = "lualatex"
 metadata-file = "metadata.yml"
+verbosity = "INFO"
 
 [output.pandoc.profile.pdf.variables]
 mainfont = "CoreSansA45.ttf"
@@ -49,8 +50,8 @@ sansfontoptions = [
 ]
 # You can get these fonts here: https://fonts.google.com/selection?query=noto+color+
 monofont = "Noto Sans Mono"
-mainfontfallback = ["Open Sans"]
-sansfontfallback = ["Open Sans"]
+mainfontfallback = ["Open Sans:style=Regular"]
+sansfontfallback = ["Open Sans:style=Regular"]
 monofontfallback = [
   "Noto Color Emoji:mode=harf",
 ]
@@ -90,8 +91,8 @@ sansfontoptions = [
 ]
 # You can get these fonts here: https://fonts.google.com/selection?query=noto+color+
 monofont = "Noto Sans Mono"
-mainfontfallback = ["Open Sans"]
-sansfontfallback = ["Open Sans"]
+mainfontfallback = ["Open Sans:style=Regular"]
+sansfontfallback = ["Open Sans:style=Regular"]
 monofontfallback = [
   "Noto Color Emoji:mode=harf",
 ]
@@ -121,8 +122,8 @@ metadata-file = "metadata.yml"
 [output.pandoc.profile.html.variables]
 # You can get these fonts here: https://fonts.google.com/selection?query=noto+color+
 monofont = "Noto Sans Mono"
-mainfontfallback = ["Open Sans"]
-sansfontfallback = ["Open Sans"]
+mainfontfallback = ["Open Sans:style=Regular"]
+sansfontfallback = ["Open Sans:style=Regular"]
 monofontfallback = [
   "Noto Color Emoji:mode=harf",
 ]
diff --git a/book/src/02_basic_calculator/08_overflow.md b/book/src/02_basic_calculator/08_overflow.md
index feaa0e9..864d096 100644
--- a/book/src/02_basic_calculator/08_overflow.md
+++ b/book/src/02_basic_calculator/08_overflow.md
@@ -80,8 +80,6 @@ The `bench` profile is the default profile used by `cargo bench`. The `bench` pr
 Use `dev` for iterative development and debugging, `release` for optimized production builds,\
 `test` for correctness testing, and `bench` for performance benchmarking.
 
-
-
 > "Have you built your project in release mode?" is almost a meme in the Rust community.\
 > It refers to developers who are not familiar with Rust and complain about its performance on
 > social media (e.g. Reddit, Twitter, etc.) before realizing they haven't built their project in