I bought a book of train tickets, but didn't use them all before they expired.
I purchased a book of rail tickets, but didn't get through them all before they were out of date.
ーI bought a book of train tickets, but didn't use them all before they expired.
「電車の回数券を買ったが、期限が切れる前に全部使わなかった」
a book of train tickets で「電車の回数券」
to expire で「（有効期限が）切れる」
ーI purchased a book of rail tickets, but didn't get through them all before they were out of date.
「電車の回数券を購入したが、期限が切れる前に全部使い終わらなかった」
a book of rail tickets で「電車の回数券」
to get through で「〜し終える」
out of date で「期限切れの・無効の」
ご参考まで！
"I bought a book of tickets, but I couldn’t use them all, so I have some left over."
"I bought a book of tickets, but I couldn’t use them all, so I have some left over."
"I bought a multi-ride ticket pass, but I didn’t use it up."
"I bought commuter tickets, but I ended up with some unused ones."
"I bought a bundle of train tickets, but I have a few left."
回数券＝book / bundle / pack of tickets が定番
・a book of tickets は、紙のチケットがまとまった「回数券」っぽさが出ます。
・a bundle of tickets / a pack of tickets も「まとめ買い」感が出て自然です。
カナダ 
アメリカ合衆国 
