I know it feels like you just picked the last Christmas tree needles from your carpet, but with Ash Wednesday one month from yesterday, it really is time to look ahead to Lent. That anticipated preparation can help ensure that the season will be a time of transformation, and not just sporadic acts of self-discipline. Lent is not just for sacrifices, of course. It is ideal for that all-round spiritual growth that comes from spending quality time in spiritual reading, which Dorothy Day called "the oil that keeps the lamps burning."
You might consider choosing one really significant book for the whole of Lent, or take the challenge of a more intense spiritual program of a book a week. (The latter sounds almost too much, but it depends on the books you choose; if you have trouble concentrating, it may actually be the more do-able!)
So, what would I recommend?
For "One Lent/One Book," you want something with real substance, something that has the power to hold your attention on several levels at once; the kind of book that you can ruminate on. My "go to" book of this sort is Hans Urs von Balthasar's amazing "Heart of the World." It's an extended meditation on the Paschal Mystery (and so eminently suitable for Lent and for the Easter Octave and beyond). The translation is sheer poetry, but above all it is the perspective that is so awe-inspiring. The point of view seems to switch between divine omniscience and an utterly, brutally honest human take that makes the awefulness of sin that much plainer. It's a book you will never want to put down; even more, you will never want to lose track of the insights it gave you.
Now, if you didn't read it last year, Pope Benedict's "Jesus of Nazareth" (vol. 2 on Holy Week and Easter) is always an option if you are up for some seriously reflective reading; on the more conversational side (something you can take in with your morning coffee), Fr. Barron's "Catholicism" would be a good way to brush up on your overall Catholic awareness. (I'd recommend this one especially if you didn't get much in the way of solid Catholic instruction growing up.)
Back in the patristic era, Lent was not just a time of preparation for Baptism; it was also a season of public penance for those whose sins had cut them off in an external way from the life of the Church. If we get ashes ourselves, it is because those public sinners accepted being marked with ashes as an outward sign that they were committed to renewing their lives: instead of just marking out the "public" sinners, the Church eventually offered everyone that sense of "solidarity." After all (as von Balthasar pointed out in "Heart of the World"), "if there is a communion of saints, there is also a communion of sinners." So Lent can be an occasion to get to know the Church better in its members. I always appreciate a good biography. If you do, too, you might choose a biography of a convert to the faith (I'm thinking maybe Dorothy Day or Abby Johnson), or one who made the essential Lenten journey from tepidity to discipleship (even someone like Teresa of Avila). Whom else might be a good Lenten companion?
You could also go with the book I am currently reading (ever so slowly), about which I have written before. I am now on page 10. This little book, under 90 pages, may yet last me through the whole of Lent. It's that packed. Lots to reflect on and apply to life here, with great potential for spiritual transformation. And isn't that one of the goals of Lent?
And then there's the old standby approach: a book of daily reflections for the season. Here's one I contributed to (try a sample). Each day's reflection is matched to one verse of the Gospel for the day, so you are praying in sync with the whole Church. That's sure in the spirit of Lent, when the "elect" are preparing to be brought fully in sync with the Church's life and prayer! (Come to think of it, that would make this a great pre-baptismal gift for an adult in RCIA!) You can also go with something pocket-sized, ideal for commuters (or for those who just don't have the time available for a 15-minute meditation).
Those are my suggestions for One Lent, One Book. What about your ideas for a (lighter) book a week for the six and a half weeks between Ash Wednesday and Good Friday?