diff --git a/books.sh b/books.sh
index 5de308f..f1f0e38 100644
--- a/books.sh
+++ b/books.sh
@@ -1,25 +1,23 @@
 # Google SRE Books.
+
+# NOTE: The indentation before inner vars should be always "tab" not "space".
 declare -A BOOKS
 BOOKS=(
 
     # Site Reliability Engineering
-    ["SRE_BOOK"]=$(
-        echo '
-            BOOK_NAME=sre-book
-            BOOK_NAME_FULL=Site Reliability Engineering
-            BOOK_FILE=google-sre-book
-            BOOK_TOC_URL=https://landing.google.com/sre/sre-book/toc/index.html
-        '
-    )
+    ["SRE_BOOK"]='
+	BOOK_NAME=sre-book
+	BOOK_NAME_FULL=Site Reliability Engineering
+	BOOK_FILE=google-sre-book
+	BOOK_TOC_URL=https://landing.google.com/sre/sre-book/toc/index.html
+	'
 
     # Site Reliability Workbook
-    ["SRW_BOOK"]=$(
-        echo '
-            BOOK_NAME=workbook
-            BOOK_NAME_FULL=The Site Reliability Workbook
-            BOOK_FILE=google-sre-workbook
-            BOOK_TOC_URL=https://landing.google.com/sre/workbook/toc/index.html
-        '
-    )
+    ["SRW_BOOK"]='
+	BOOK_NAME=workbook
+	BOOK_NAME_FULL=The Site Reliability Workbook
+	BOOK_FILE=google-sre-workbook
+	BOOK_TOC_URL=https://landing.google.com/sre/workbook/toc/index.html
+	'
 
 )
diff --git a/bootstrap.sh b/bootstrap.sh
index f9f06b3..79af46b 100755
--- a/bootstrap.sh
+++ b/bootstrap.sh
@@ -3,13 +3,13 @@ if [[ "${DEBUG}" == 1 ]]; then
     set -x
 fi
 set -euo pipefail
+IFS=$'\n\t'
 
 # Get book details.
 source books.sh
 export ${BOOKS[${BOOK_SLUG^^}]}
 
 # Common vars.
-IFS=$'\n\t'
 IMGS_DOMAIN="lh3.googleusercontent.com"
 
 #
@@ -20,6 +20,7 @@ IMGS_DOMAIN="lh3.googleusercontent.com"
 # Enable recursion, timestamping (--mirror)
 # Images are hosted elsewhere, download them as well.
 # We need to go up a level from /toc/ where we start
+# The "ture" at the end to ignore non-200 URLs like 404.
 wget \
     --convert-links         \
     --directory-prefix=html \
@@ -31,7 +32,7 @@ wget \
     --mirror                \
     --no-verbose            \
     --recursive             \
-    --domains=${IMGS_DOMAIN},landing.google.com ${BOOK_TOC_URL}
+    --domains=${IMGS_DOMAIN},landing.google.com ${BOOK_TOC_URL} || true
 
 #
 echo "Get working mode..."