We can read this text, as it isn't difficult

We could read English books last year.

The modal phrase be able to is used to supply the missing tense forms of the infinitive:

We have been able to come in time because we took a bus.

We'll be able to help you as soon as we finish this exercise.

I'd like to be able to help you.

The phrase be able to differs from the verb can in its meaning. The verb can expresses permanent ability, while be able to combines ideas of ability and achievement; it also expresses ability due to circumstances:

We could do it, but didn't want to.

We were able to do it, because you helped us.

The phrase ‘ used to be able to do something ’ means ‘could before but can no longer’:

When a boy, he used to be able to run faster than anybody.

The phrase able to and the verb manage can be used when speaking about one specific action in the past:

He was able (managed) to come yesterday because he was free.

The form ‘ could + non-perfect infinitive ’ is used to express hypothetical ability in the present or future. The form ‘ could + perfect infinitive’ is used to express hypothetical ability in the past:

I could come earlier if there were a train in the morning.

He could have written to you if he had known your address.

2. The verb can is used with non-perfect infinitive to denote possibility:

a) General possibility

In this case we say that situations are possible theoretically or in general:

Don’t get upset – the weather can change for the better.

We thought he could be busy and didn’t call him.

b) Possibility due to circumstances:

His pictures cannot be exhibited here, as they are too extravagant.

John can be on his way home already. He doesn’t stay in the office after 5.

c) Possibility due to the existing laws, rules, regulations:

You can borrow books from the library if you need them.

d) Phrases “ can’t help something ” and “ can’t help doing something ” are used when we want to say that we do something in spite of ourselves:

I was late again. But I couldn’t help it.

I couldn’t help overhearing them – they were talking too loudly.

Phrases “ cannot do but ” and “ could not do but ” are used to emphasize the only possible thing to do:

What could we do but tell her the truth?

3. The verb could is used to express hypothetical possibility and the time reference is expressed by the form of the infinitive of the notional verb:

You could still see them here walking hand in hand.

You could have heard her singing there.

4. The verb can with non-perfect infinitive is used when asking for permission, granting or denying permission:

- asking for permission: Can I pass here?

- granting permission: Yes, you can. Everybody goes this way.

- denying permission: No, you can't. The path is to your left.

Both can and could are used in reported speech when we talk about the permission already given or refused, and about things that are (or are not) allowed by laws or rules:

They said we could enter whenever we came.

I don’t think we can park here – there is a sign.

The past form of the phrase be allowed is used when we talk about permission for one particular action in the past:

We were allowed to enter though we were late.

5. The negative form of can with non-perfect infinitive is used to express prohibition, which is determined by laws, situation or natural state of things:

You cannot cross the street when the street light is red.

6. Both can and could are used to express request, could being more polite: