Learn Swedish: Jag läser ibland boken i sängen. - I sometimes read the book in bed.

In Swedish main sentences, frequency adverbs like ibland (sometimes) come directly after the first verb. In English, we usually put 'sometimes' before the verb ('I sometimes read'), but Swedish strictly follows the Subject-Verb-Adverb order here: Jag läser ibland.

Can I put ibland at the very beginning of the sentence instead?

Yes! But remember the Swedish V2 rule, which says the verb must be the second piece of information. If you start with Ibland, the verb läser must come right next, followed by the subject: Ibland läser jag boken i sängen.

Why does it say i sängen (in the bed) instead of just i säng?

Swedish often uses the definite form (adding -en to make it 'the bed') for everyday locations where English drops the article. So while English says 'in bed', Swedish naturally says i sängen.

Just a refresher: how does boken mean 'the book'?

In Swedish, the word 'the' is attached to the end of the noun. The base word is en bok (a book). To make it definite ('the book'), you drop the en from the front and stick it on the end to get boken.